EPA/530-SW-86-007-F
DESIGN, CONSTRUCTION, AND EVALUATION OF CLAY LINERS
          FOR WASTE MANAGEMENT FACILITIES
                         by
          L.J. Goldman and L.I. Greenfield
                  NUS Corporation
           Gaithersburg,  Maryland  20878

             A.S.  Damle,  G.L.  Kingsbury
         C.M. Northeim,  and R.S. Truesdale
            Research Triangle  Institute
   Research Triangle Park, North Carolina  27709
            EPA Contract No.  68-01-7310
                  Project Officer

                    M.H.  Roulier
          Waste Minimization,  Destruction
           and Disposal  Research Division
       Risk Reduction Engineering Laboratory
              Cincinnati, Ohio  45268
             OFFICE OF SOLID WASTE AND
                 EMERGENCY RESPONSE
        U.S.  ENVIRONMENTAL PROTECTION AGENCY
               WASHINGTON, DC  20460
       RISK REDUCTION ENGINEERING LABORATORY
         OFFICE OF RESEARCH AND DEVELOPMENT
        U.S.  ENVIRONMENTAL PROTECTION AGENCY
              CINCINNATI,  OHIO  45268

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                                DISCLAIMER
     The Information in this document has been funded wholly by the United
States Environmental Protection Agency under Contract 68-03-3149 to Research
Triangle Institute, Research Triangle Park, North Carolina and Contract
68-01-7310 to NUS Corporation, Gaithersburg, Maryland.  It has been subject
to the Agency's peer and administrative review, and it has been approved for
publication as an EPA document.  Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
                                    it

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                                   FOREWORD
      Today's  rapidly  developing  and  changing technologies and  industrial
 products  and  practices  frequently  carry with them the  increased generation
 of materials  that,  if improperly dealt with, can threaten both public
 health  and  the  environment.  The U.S. Environmental Protection Agency  is
 charged by  Congress with  protecting  the Nation's land, air, and water
 systems.  Under a mandate of national environmental laws, the  agency strives
 to formulate  and implement actions leading to a compatible balance between
 human activities and  the  ability of  natural systems to support and nurture
 life.   These  laws direct  the EPA to  perform research to define our environ-
 mental  problems, measure  the impacts, and search for solutions.

     The  Risk Reduction Engineering  Laboratory is responsible  for planning,
 implementation,  and management of  research, development, and demonstration
 programs  to provide an  authoritative, defensible engineering basis in
 support of the  policies,  programs, and regulations of the EPA with respect
 to drinking water, wastewater, pesticides, toxic substances, solid and
 hazardous wastes, and Superfund-related activities.  This publication  is
 one of  the products of  that research and provides a vital communication
 link between  the researchers and the user community.

     The Office  of Solid  Waste is  responsible for issuing regulations  and
 guidelines on the proper  treatment,  storage, and disposal of hazardous
 wastes  to protect human health and the environment from the potential harm
 associated with  improper  management  of these wastes.  These regulations are
 supplemented  by  guidance  manuals, technical guidelines, and technical
 resource documents, made  available to assist the regulated community and
 facility designers in understanding  the scope of the regulatory program.
 Publications  like this one provide facility designers with state-of-the-art
 information on design and performance evaluation techniques.

     This technical resource document is a compilation of all of the available
 information relevant to the design, construction, and performance of clay-
 lined waste management facilities.  The broad topics covered are: clays;
 geotechnical  testing of soils; the compatibility of clays and chemical
 wastes; the design, construction, and construction* quality assurance of
.clay liners;  potential failure mechanisms; the performance of existing
 facilities; and methods for predicting the useful life (transit time) based
 on the modeling of leachate flow through soils.
                                  E. Timothy Oppelt, Acting Director
                                  Risk Reduction Engineering Laboratory

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                                   PREFACE   .


      Subtitle C of the Resource Conservation and  Recovery Act  (RCRA)  requires
 the U.S.  Environmental Protection Agency (EPA)  to establish a  Federal hazard-
 ous waste management program.   This  program must  ensure  that hazardous wastes
 are handled safely from generation until  final  disposition.  EPA  issued a
 series  of hazardous waste regulations  under Subtitle C of RCRA that are
 published in 40 Code of Federal  Regulations  (CFR)  260 through  265 and 122
 through 124.

      Parts 264 and 265 of 40 CFR contain  standards applicable  to owners and
 operators of all  facilities that treat,  store,  or dispose of hazardous
 wastes.  Wastes are identified  or listed  as hazardous under 40 CFR Part 261.
 Part 264  standards are implemented through permits issued by authorized
 States  or EPA according to 40 CFR Part 122 and  Part 124  regulations.  Land
 treatment,  storage, and disposal  (LTSD)  regulations in 40 CFR  Part 264 issued
 on  July 26,  1982,  establish performance  standards  for hazardous waste land-
 fills,  surface impoundments, land treatment units, and waste piles.

      EPA  is  developing three types of documents for preparers  and reviewers
 of  permit applications for hazardous waste LTSD facilities.  These types
 include RCRA Technical  Guidance  Documents, Permit  Guidance Manuals, and
 Technical  Resource Documents (TRD's).                                 \

      The  RCRA Technical  Guidance  Documents present design and  operating
 specifications or  design evaluation techniques  that generally  comply with or
 demonstrate  compliance with the  Design and Operating Requirements and the
 Closure and  Post-Closure Requirements of  Part 264.

      The  Permit Guidance Manuals  are being developed.to describe the permit
 application  information the Agency seeks  and to provide guidance to appli-
 cants and permit writers in addressing information requirements.  These
 manuals will  include a discussion  of each step  in  the permitting process and
 a description  of each  set of specifications that must be considered for
 inclusion in  the permit.

     This document is  a Technical  Resource Document.  It was prepared by the
 Hazardous Waste Engineering Research Laboratory of the Office  of Research and
 Development at the request of and  in cooperation with the Office of Solid
 Waste and Emergency Response.  The TRD was first  issued as a draft for public
 comment under  the  title,  "Design,  Construction, and Evaluation of Clay Liners
 for Waste Management Facilities"  (EPA/530-SW-86-007) dated March 1986.  The
 draft TRD was  also made available  through the National  Technical  Information
 Service (Order No.  PB86-184496/AS).  All  comments  received on the draft TRD
 have been carefully considered and, if appropriate, changes were made in this
 final document  to  address  the public's concerns.  With  issuance of this docu-
ment, all previous  drafts  of the TRD are obsolete and should be discarded.
                                      IV

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                                     ABSTRACT

                              .Z- ^  '•' '  -  ' -.&• -•"&
     This Technical Resource Document (TRD) is a compilation of an of the
available information on the design, construction, and evaluation of clay
liners for waste landfills, surface impoundments, and wastepiles.  The
information was obtained from the literature and from in-depth interviews
with design and construction engineers and other knowledgeable individuals in
both the private and government sectors.   As a consequence, some information
is presented for the first time in this document.  The broad topics covered
are:  clays, with emphasis on their composition, fabric, and hydraulic con-
ductivity; geotechnical test methods and soil properties including index
properties, soil classification, and hydraulic conductivity testing; clay
chemical compatibility, including a discussion of the mechanisms of interac-
tion and a comprehensive compilation of existing test data from the litera-
ture and private sources; construction and quality assurance; clay liner
failure mechanisms; the performance of existing clay liners based on case
studies of 17 sites; and clay liner transit time prediction methods featuring
an in-depth discussion of many available techniques and models.

     This TRD was submitted in September 1987 by NUS Corporation in fulfill-
ment of Contract No. 68-01-7310 with the U.S. Environmental Protection
Agency.  The TRD has been revised to address issues that were raised during
the public comment period on the draft TRD (EPA/530-SW-86-007); the revised
TRD also includes technical information that became available after the draft
TRD was completed by the Research Triangle Institute 1n August 1985.

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                              TABLE OF CONTENTS


Chapter                                                                 Page

          Foreword	  iii
          Preface	  1 v
          Abstract	  v
          Figures	„..  Xiv
          Tables	..„..  Xix
          Acknowledgments	„. J  xxi i

   1      Introduction	„..  i-i
          1.1  Scope	„..  i_3
          1.2  Summary of Current Practices	  1-3
               1.2.1   Investigation of Site Conditions
                       (Field)	  1-3
               1.2.2   Material  Selection and Characterization
                       (Laboratory)	  1-4
               1.2.3   Develop Liner Design/Construction
                       Plans	  1-5
               1.2.4   Pilot Construction Test (Test Fill)	  1-5
               1.2.5   Construction	  1-5
          1.3  Analysis of Current Practices	  1-7
               1.3.1   Liner Material	  1-7
               1.3.2   Clod Size	  1-7
               1.3.3   Water Content	  i-a
               1.3.4   Pilot Construction (Test Fill)	  1-8
          1.4  Summary	  i_g
          1.5  Reference	  i_g

   2      Clay Soil  	....!  2-1
          2.1  Clay  Minerals 	....'  2-2
               2.1.1   Clay Mineral  Structure	  2-2
               2.1.2   Clay Mineral  Groups	  2-4
                       2.1.2.1   Kaolinite Minerals	  2-4
                     .  2.1.2.2   Illite Minerals 	*.....  2-9
                       2.1.2.3   Chlorite Minerals	  2-10
                       2.1.2.4   Smectite Minerals ..-.	  2-13
          2.2  Clay  Formation and Occurrence	  2-14
               2.2.1   Clay Mineral  Paragenesis 	  2-14
               2.2.2   Clay Soil  Formation and Occurrence	  2-15
                       2.2.2.1   Fluvial  Soils	  2-16
                       2.2.2.2   Glacial  Soils	  2-17
                       2.2.2.3   Residual  Soils 	.........  2-17
          2.3  Clay  Chemistry	  2-18
               2.3.1    Electrical  Double-Layer Theory	  2-18
               2.3.2   Cation-Exchange  Capacity and Cation
                       Affinity	  2-20
               2.3.3    Significance  of  the Electrical Double
                       Layer to Clay Liners	   2-22
                                     VI

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Chapter
                        TABLE OF CONTENTS (continued)
                                                                        Page

          2.4  Clay Soil Fabric and Hydraulic Conductivity	  2-24
               2.4.1   Soil Porosity and Hydraulic
                       Conductivity	  2-24
                       2.4.1.1   Soil  Microstructure and Primary
                                 Porosity	  2-24
                       2.4.1.2   Soil  Macrostructure and Secondary
                                 Porosity 	  2-27
               2.4.2   Sail Structure  and Hydraulic
                       Conductivity in Compacted Soils  	  2-32
          2.5  References	  2-38

          Test Methods and Soil  Properties 	  3-1
          3.1  Introduction	  3_i
          3.2  Fundamental  Relationships	'/.'.'.  3-2
               3.2.1   Water Content	  3_2
               3.2.2   Density	  3_2
               3.2.3   Specific  Gravity 	  3_2
               3.2.4   Unit Weight	    3.5
               3.2.5   Void Ratio 	  3.5
               3.2.6   Porosity	  3.5
               3.2.7   Degree of Saturation  	!  3-6
          3.3  Atterberg Limits  	  3_6
          3.4  Soil  Classification	  3-10
               3.4.1   Grain Size Analysis 	  3-10
               3.4.2   The Unified  Soil  Classification System	  3-15
                       3.4.2.1   Field Classification	  3-15
                       3.4.2.2   Laboratory  Classification  	  3-17
                       3.4.2.3   Field Identification Procedures for
                                 Fine-Grained Soils  or Fractions ....    3-19
          3.5  Compaction	  3_2Q
               3.5.1   Fundamentals  of Compaction  	!!!!!  3-20
               3.5.2   Compaction and  Permeability	  3-25
          3.6  Field Measurement of  Density  and  Moisture
               Content 	   3_2*;
               3.6.1   Traditional Methods	   3-25
               3.6.2   Nuclear Methods	   3-28
                       3.6.2.1    Nuclear Density Gauge 	   3-28
                       3.6.2.2    Nuclear Moisture Gauge	   3-31
          3.7   Testing  for  Shear Strength	   3-33
          3.8   Hydraulic  Conductivity Testing	   3-35
               3.8.1    Darcy's Law	   3-36
               3.8.2    Hydraulic  Gradient  	   3-38
               3.8.3    Permeability Measurement and Factors
                       That  Influence Test Results	  3-39
                       3.8.3.1   Sample Selection, Size,  and
                                Preparation 	  3-40
                      3.8.3.2   Hydraulic Gradient	  3-45
                      3.8.3.3   Sample Saturation 	  3-47
                                    vii

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                        TABLE OF CONTENTS (continued)

Chapter

                       3.8.3.4   Permeant Characteristics	  3-49
                       3.8.3.5   Test Duration 	«...  3-49
               3.8.4   Laboratory Permeability Tests	  3-50
                       3.8.4.1   Pressure Cell	  3-50
                       3.8.4.2   Compaction Permeameter	.......  3-50
                       3.8.4.3   Triaxial Cells	  3-55
                       3.8.4.4   Consolidation Cells	  3-57
               3.8.5   Field Permeability Tests	.......'  3-57
                       3.8.5.1   Bore Hole Tests 	....  3-57
                       3.8.5.2   Porous Probes	  3-61
                       3.8.5.3   Air Entry Permeameter ...............  3-63
                       3.8.5.4   The Guelph Permeameter ...............  3-66
                       3.8.5.5   Ring Infiltrometers	  3-69
          3.9  References	  3-73

   4      Clay-Chemical Interactions and Soil  Permeability ............  4-1
          4.1  Parameters Determined in Permeability
               Testing for Compatibility	  4-2
          4.2  Clay-Chemical Interactions that Influence
               Permeability	  4-3
               4.2.1   Soil Fabric and Permeability	  4-4
               4.2.2   Dissolution by Strong Acids or Bases ..........  4-11
               4.2.3   Precipitation of Solids	  4-11
               4.2.4   Effect of Microorganisms	  4-11
          4.3  Measuring Clay-Chemical Compatibility
               Through Permeability Testing	  4-12
               4.3.1   Measurement Devices	  4-12
               4.3.2   Test Setup	  4-13
               4.3.3   Compatibility of Materials With Test
                       Fluids	  4-13
               4.3.4   Effect of Backpressure	  4-14
               4.3.5   Effect of Hydraulic Gradient	  4-14
               4.3.6   Criteria for Concluding a Test	  4-15
          4.4  Summary of Available Research Data ...«.	  4-16
          4.5  Permeability Studies To Investigate Clay-Chemical
               Interactions (test methods, data, and discussion of
               results for 23 individual studies)	  4-16
               4.5.1   Observations by Macey (1942) on
                       Effects of Organics on Fireclay	  4-16
               4.5.2   Tests With Kaolinite and Organic
                       Solvents by Michaels and Lin (1954) 	  4-26
               4.5.3   Study by Buchanan (1964) of the Effect
                       of Naphtha on Montmorillonite	  4-29
               4.5.4   Study by Reeve and Tamaddoni (1965)
                       of the Effect of Electrolyte
                       Concentration on Permeability of a
                       Sodic Soil	  4-29
                                    viii

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                        TABLE OF CONTENTS (continued)

Chapter      "                ,:,  ;;|,v    ' ; 4*, 14                         Page

               4.5.5   Tests by van Schaik and Laliberte (1968)
                       of Permeability of Soils to a Liquid
                       Hydrocarbon	„	  4_31
               4.5.6   Study by Everett (1977)  of Permeability
                       of Lacustrine Clay to Four Liquid Wastes 	  4-32
               4.5.7   Tests by Sanks and Gloyna (1977) of
                       Permeability of Lacustrine Clay to
                       Liquid Waste	  4.33
               4.5.8   Investigation of the  Effect of
                       Organic Solvents on Clays by
                       Green, Lee,  and Jones (1979) 	  4-35
               4.5.9   Anderson's Study (1981)  of the Effects
                       of Organics  on Permeability 	  4-39
               4.5.10  Schramm's  Study (1981) of the
                       Permeability of Soil  to  Organic Solvents 	  4-54
               4.5.11  Evaluation by Monserrate (1982)
                       of the Permeability of Two Clays to
                       Selected Electroplating  Wastes	  4-59
               4.5.12  Research by  Brown,  Green,  and Thomas
                       (1983)  on  the  Effect  of  Two Organic
                       Hazardous  Wastes on Simulated Clay Liners  	  4-60
               4.5.13  Study by Brown,  Thomas,  and Green
                       (1984)  of  the  Effect  of  Dilutions
                       of Acetone and Mixtures  of Xylene
                       and Acetone  on Permeability of a
                       Micaceous  Soil	  4.54
               4.5.14  Tests by Brown,  Thomas,  and Green
                       (1984)  to  Determine the  Permeability
                       of Micaceous Soil to  Petroleum Products  	  4-64
               4.5.15  Study by Brown and  Thomas  (1984) of
                       the Permeability of Commercially
                       Available  Clays  to  Organics  	  4-70
               4.5.16  Studies Conducted for  EPA  by Daniel
                       (1983)  and Foreman  and Daniel  (1984)
                       at  the  University of Texas,  Austin 	  4-72
               4.5.17  Tests Conducted  for Chemical
                       Manufacturers  Association  by Daniel
                       and Liljestrand  (1984)	  4-73
               4.5.18  Study by Dunn  (1983) of  the  Effects
                       of  Synthetic Lead-Zinc Tailings
                       Leachate on Clay Soils 	  4-81
               4.5.19  Studies by Acar  and Others  (1984)  on the
                       Effect of  Organics  on Kaollnite  	   4-82
               4.5.20   Finding by Olivieri (1984) of
                       Impermeability of Montmorillonite  to
                       Benzene	   4_8-:}
              4.5.21   Study of Permeability of Clays to
                       Simulated  Inorganic Textile Wastes
                      by Tulis (1983)  	   4_84
                                    IX

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                        TABLE OF CONTENTS (continued)

Chapter                                                                 Page

               4.5.22  Tests Conducted by Engineering
                       Consulting Firms for Specific Applica-
                       tion (unpublished data) 	....,,	  4-84
               4.5.23  Tests Reported by Bentonite Companies	  4-94
          4.6  References 	.	...	  4-93

   5      Current Practices:  Clay Liner Design and Installation 	  5-1
          5.1  Design	  5-1
               5.1.1   Site Investigation	  5-2
               5.1.2   Liner Material Selection and
                       Characterization	  5-6
                       5.1.2.1   Native Soils	  5-13
                       5.1.2.2   Admixed Soils	  5-14
               5.1.3   Facility Design	  5-16
                       5.1.3.1   Configuration	  5-16
                       5.1.3.2   Foundation Design	  5-16
                                 5.1.3.2.1   Settlement	  5-16
                                 5.1.3.2.2   Seepage	  5-17
                                 5.1.3.2.3   Dike Design	  5-18
                                 5.1.3.2.4   Sidewall Design 	..  5-21
                                 5.1.3.2.5   Bottom Design	  5-27
                       5.1.3.3   Liner Design	  5-27
                       5.1.3.4   Special  Design Considerations	  5-32
                                 5.1.3.4.1   Control of Erosion 	  5-32
                                 5.1.3.4.2   Control of Scouring 	  5-33
                                 5.1.3.4.3   Cold Climate Design 	  5-34
                                 5.1.3.4.4   Control of Piping	  5-34
                                 5.1.3.4.5   Control of Desiccation ..  5-35
                                 5.1.3.4.6   Seismic Design ...»	  5-35
                                 5.1.3.4.7   Intergradient Facility
                                             Design 	.....	  5-39
               5.1.4   Construction Specifications and CQA Plan ......  5-40
               5.1.5   Design Case Studies 	.	  5-42
          5.2  Clay Liner Construction:   Methodology -
               and Equipment	„	  5-46
               5.2.1   Preinstallation Activities	  5-46
                       5.2.1.1   Foundation Preparation	  5-46
                       5.2.1.2   Groundwater Control  	.	  5-47
                       5.2.1.3   Leak Detection System Installation ..  5-48
               5.2.2   Clay Liner Installation	  5-48
                       5.2.2.1   Natural  Soil  Liners	  5-48
                                 5.2.2.1.1   Liner Material
                                             Emplacement .............  5-49
                                 5.2.2.1.2   Clod Size Reduction	5-49
                                 5.2.2.1.3   Moisture Control  .„	  5-52
                                 5.2.2.1.4   Compaction	  5-55
                       5.2.2.2   Admixed  Bentonite Liners	  5-70
                       5.2.2.3   Climatic Effects	  5-75
               5.2.3   Postinstallatlon Activities	  5-80

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                        TABLE OF CONTENTS (continued)

Chapter      "                i4i-**.-\-"J    ^..r.                         Page
5.3 Quality Assurance and Quality Control 	
5.3.1 Key Terms 	 	 	 	 	
5.3.2 Personnel 	 	 	
5.3.3 Observations and Tests 	 	 	
5.3.4 Documentation 	 	
5.4 Clay Liner Design and Construction: Problems
and Preventive Measures 	
5.5 References 	 	 	 	 	
Failure Mechanisms 	 	 	 	 	 	
6.1 Desiccation Cracks 	 	
6.1.1 Description 	 	 	
6.1.2 Studies of Cracking 	
6.2 Slope Instability 	 	 	
6.2.1 Description 	 	
6.2.2 Discussion of Slope Instability 	
6.3 Settlement 	 	 	
6.3.1 Description 	
6.3.2 Studies of Settlement 	
6.4 Piping 	
6.4.1 Description 	 „ 	
6.4.2 Studies of Piping 	 	 	
6.5 Penetration 	 	 „ 	
6.5.1 Description 	 	 	 „ 	
6.5.2 Studies of Penetration 	 	 	

6.6.1 Description 	 	 	
6.7 Cold Climate Operations 	 	 	 	 	
6.8 Earthquakes 	
6.9 Scouring 	
6.10 Failures from Design or Construction Errors 	
6.11 References 	 	 	 	 	
Clay Liner Performance 	
7.1 Introduction 	 i 	
	 5-82
	 5-83
, . . . . 5-86
, . . . . 5-88
..... 5-98

..... 5-109
	 5-112
	 6-1
	 6-1
	 6-1
	 6-2
	 6-3
.... 6-3
.... 6-4
.... 6-5
	 6-5
	 6-5
.... 6-6
	 6-6
	 6-6
	 6-8
.... 6-8
.... 6-9
	 6-9
.... 6-9
.... 6-9
.... 6-11
.... 6-15
.... 6-16
	 6-17
.... 7-1
	 7-1
         7.2  Case Studies  (physical description; startup date;
              geology and hydrology; waste type; liner description,
              installation, and performance for 17 clay-lined
              "   	                                              7-1
                                                                       7-2
                                                                       7-5
                                                                       7-7
                                                                       7-9
                                                                       7-14
                                                                       7-18
                                                                       7-21
                                                                       7-25
                                                                       7-28
                                                                       7-33
                                                                       7-38
                                    xi
7.2.1
7.2.2
7.2.3
7.2.4
7.2.5
7.2.6
7.2.7
7.2.8
7.2.9
7.2.10
7.2.11
Criteria
Site A .,
Site B .,
Site C .,
Site D .,
Site E .,
Site F ..
Site 6 ..
Site H .,
Site I ..
Site J ..
for Site Selection 	











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                        TABLE OF CONTENTS  (continued)
Chapter
Page
                7.2.12   Site  K		....  7-42
                7.2.13   Site  L	  7-46
                7.2.14   Site  M	  7-49
                7.2.15   Site  N	  7-55
                7.2.16   Site  0	  7-59
                7.2.17   Site  P			  7-62
                7.2.18   Site  Q	  7-67
          7.3   Liner Types	  7-70
                7.3.1    Unlined  Facilities	  7-71
                7.3.2    Recompacted Soil Liners	  7-72
                7.3.3    Admixed  Liners	  7-72
          7.4   Site Characterization  	.	....'  7-73
                7.4.1    Case  Studies	  7-74
          7.5   Installation  of  Clay Liners	  7-74
                7.5.1    Installation Methods  	.........  7-75
                7.5.2    Quality  Assurance/Quality Control
                        for Clay Liners	.......  7-76
          7.6   Waste Types  	.......  7-77
                7.6.1    Free  Liquids	  7-77
                7.6.2    Stabilized or Solidified Liquids ..............  7-78
                7.6.3    Sludges  and Solid Wastes ..	  7-78
                7.6.4    Waste Compatibility  	.......  7-79
          7.7   Performance Monitoring	  7-81
                7.7.1    Unsaturated Zone Monitoring	  7-82
                7.7.2    Groundwater Monitoring 	.......:  7-84
                7.7.3    Leachate Level and Quality
                        Monitoring	  7-85
          7.8   Conclusions  	.	  7-85
          7.9   References	  7-86

   8      Prediction of Clay Liner Performance	  8-1
          8.1   Introduction	  8-1
          8.2   Background Considerations 	.......  8-1
                8.2.1    Performance Criteria  	—	,..«,...  8-1
                8.2.2    Clay  Liner System 	.......  8-2
                8.2.3    General  Equations	  8-4
          8.3   Transit  Time  Prediction Methods	.„...;  8-6
                8.3.1    Simple Transit Time  Equation	.......  8-6
                8.3.2    Modified Transit Time Equation	  8-8
                8.3.3    Green-Ampt Wetting Front Model 	„..   8-9
                8.3.4    Transient Linearized  Infiltration
                        Equation	  8-10
                8.3.5    Numerical Solutions	„...  8-12
          8.4   Comparison of Different Approaches .;	  8-14
          8.5   Batch-Type Absorption Procedures for  Estimating
                Clay Liner Performance  	,..„...  8-14
          8.6   References	  8-16

Appendix
   A      Test  Method Descriptions	  A-l
                                     xii

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                                    FIGURES

Number                         v;'f'i  '     ,'»•$-•..*?                         Page

 1-1     Cross section of an idealized clay liner system 	  1-2

 2-1     Clay mineral tetrahedral  sheet structure 	  2-3
 2-2     Clay mineral octahedral  sheet structure  	  2-3
 2-3     Kaolinite group minerals	  2-7
 2-4     mite clay minerals	  2-11
 2-5     Chlorite and smectite clay minerals 	  2-1?
 2-6     Electrical  double layer	  2-19
 2-7     Effect of solution pH on  clay mineral  surface
         charge (EPM) 	  2-21
 2-8     Comparisons of clay mineral  sizes and  surface areas  	  2-23
 2-9     Clay soil  fabrics 	  2-25
 2-10    Fractures in glacial  till	  2-28
 2-11    Root cast in glacial  till	  2-29
 2-12    Permeable strata in glacial  till  deposit	  2-30
 2-13    Compaction  curve from a standard  compaction  test  	  2-33
 2-14    Compaction  curves for different compactive efforts
         applied to  a silty clay	  2-34
 2-15    Permeability as a function  of  molding  water  content
         for  samples of silty  clay  prepared to  constant
         density by  kneading compaction 	  2-36
 2-16    The  effect  of dispersion on  hydraulic  conductivity 	  2-37
 2-17    Effect of method of compaction on the  permeability
         (hydraulic  conductivity) of  a  silty clay 	  2-39

 3-1      Schematic representation of  soil  illustrating  the
         fundamental  relationships  among the solid, liquid,
         and  air constituents	  3-4
 3-2      Consistency limits of cohesive soils	  3-6
 3-3      Device for  determining the  liquid limits of  a
         cohesive soil.   The dish contains a grooved  sample 	  3-7
 3-4      Clay sample being grooved  for  liquid limit test 	  3-7
 3-5      Rolling a clay sample for  plastic limit  test	  3-9
 3-6      Results of  rolling clay with moisture  content  below
         the  plastic limit 	  3_9
 3-7      Typical  relationships between  the liquid limit
         and  the plasticity index for various soils 	  3-11
 3-8      Idealized particle size distribution curves  for
         well-graded,  poorly-graded,  and gap-graded soils  	  3-14
 3-9      Unified soil  classification  chart 	  3-16
 3-10    Typical  soil  compaction curve  illustrating maximum
         dry  density and optimum water  content  	  3-21
 3-11    Compaction  curves for different compactive efforts
         applied to  a  silty clay	  3-23
 3-12    Four types  of compaction curves found  from
         laboratory  investigation	   3-24
 3-13    Permeability  as  a function of  molding water  content
         for  samples of  silty  clay prepared  to  constant density
         by kneading compaction 	   3-26
                                   xiii

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                             FIGURES (continued)                     ;

Number                                                                  Page

 3-14    Influence of the method of compaction on the
         permeability of silty clay	   3-27
 3-15    Schematic diagram of triaxial  compression apparatus
         for Q test	   3-34
 3-16    Effect of backpressure on permeability to water,
         Sasumua clay	   3-48
 3-17    Apparatus for pressure cell method	   3-51
 3-18    Modified compaction permeameter	   3-53
 3-19    Detail of the base plate for a double-ring permeameter 	   3-54
 3-20    Schematic of a constant head triaxial cell permeameter ......   3-56
 3-21    Consolidation permeameter	   3-58
 3-22    Two-stage, borehole permeability text (Boutwell and
         Derick, 1986)	   3-59
 3-23    Installed porous probe (Daniel, 1987)	   3-62
 3-24    Modified air-entry permeameter	   3-64
 3-25    Schematic diagram of Guelph permeameter	   3-67
 3-26    Double-ring infiltrometer	   3-70
 3-27    Sealed double-ring infiltrometer	   3-72

 4-1     Change in a pore diameter (400%) corresponding  to  a
         permeability increase of 25,600%	   4-5
 4-2     Distribution of ions adjacent  to a clay surface
         according to the concept of the diffuse double  layer  ........   4-7
 4-3     Intrinsic permeabilities as a  function of void  space
         (e)  measured for different permeants	   4-28
 4-4     Coefficient of permeability of Ranger shale to
         various chemicals	„..;   4-40
 4-5   ,  Permeability of the four clay  soils to water
         (0.01N CaS04)	   4-43
 4-6     Permeability of the four clay  soils to acetic acid ..........   4-44
 4-7     Permeability and breakthrough  curves  of the four
         clay soils treated with aniline	   4-45
 4-8     Permeability of the four clay  soils to ethylene glycol  ......   4-46
 4-9     Permeability of the four clay  soils to acetojie	   4-47
 4-10    Permeability of the four clay  soils to methanol
         and  the breakthrough curve for the methanol-treated
         mixed cation illitic clay soil	   4-48
 4-11    Permeability of the methanol-treated  mixed cation
         illitic clay soil, at two hydraulic gradients	   4-49
 4-12    Permeability and breakthrough  curves  of the four
         clay soils treated with xylene	   4-50
 4-13    Permeability and breakthrough  curves  of the four
         clay soils treated with heptane	   4-51
 4-14    Variation of intrinsic permeability with solvent
         for  each soil	   4-58
 4-15    Permeability of White Store clay to 0.01 N calcium
         sulfate, chromic acid (1 molar), and  zinc chloride
         (1 molar) as a function of moisture at compaction	   4-61
                                    xiv

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                             FIGURES (continued)

Number                         'I'^F      ;':|.  »                         page

 4-16     Hydraulic conductivity versus pore volume for
          laboratory-compacted micaceous soil  exposed to
          kerosene at a hydraulic gradient of 91 	   4-65
 4-17     Hydraulic conductivity versus pore volume for
          laboratory-compacted micaceous soil  exposed to
          diesel  fuel at a hydraulic gradient of 91 	   4-66
 4-18     Hydraulic conductivity versus pore volume for
          laboratory-compacted micaceous soil  exposed to
          paraffin oil  at. a hydraulic gradient of 91 	   4-67
 4-19     Hydraulic conductivity versus pore volume for
          laboratory-compacted micaceous soil  exposed to
          gasoline at a hydraulic gradient of 91 	   4-68
 4-20     Hydraulic conductivity versus pore volume for
          laboratory-compacted micaceous soil  exposed to
          motor oil  at a hydraulic gradient of 91 	   4-69
 4-21     Permeability versus number of pore volumes of flow
          for kaolinite permeated with methanol  at a hydraulic
          gradient of 250 or 300 	   4-74
 4-22     Permeability versus hydraulic gradient for kaolinite
          permeated in flexible-wall  permeameters	   4-75
 4-23     Permeability versus hydraulic gradient for kaolinite
          permeated in consolidation cell  permeameters	   4-76
 4-24     Permeability versus hydraulic gradient for kaolinite
          permeated in compaction mold cell  	   4-77

 5-1      Compacted clay cutoff seal  	   5-19
 5-2      Dike components and typical  configurations 	   5-20
 5-3      Methods of liner sidewall  compaction 	   5-22
 5-4      Liner design for collection system pipes and sump  	   5-28
 5-5      Methods of keying-in liner segments	   5-30
 5-6      Liner material  emplacement	   5-50
 5-7      Emplacement of liner material  over foundation
          excavation underneath a collection pipe	   5-51
 5-8      Use of pulvi-mixer for clod size reduction 	   5-54
 5-9      Moisture addition to liner material  prior to
          compaction	   5_56
 5-10     Joints  and seepage along lift boundaries	   5-61
 5-11     Sketches of different types  of roller  feet	   5-65
 5-12     Various compacting rollers	.....^...   5-67
 5-13     Compaction on a 2(H)  to 1(V)  slope with a towed
          sheepsfoot roller	   5-69
 5-14     Central  plant mixing  of bentonite  and  soil  	   5-72
 5-15     Truck-loaded  bentonite spreader  	   5-73
 5-16     Pneumatically fed bentonite  spreader	   5-76
 5-17     Blending bentonite with soil  using a disk  harrow	   5-78
 5-18     Soil  stabilizer mixing bentonite  in  place  	   5-79
 5-19     Inflatable dome over  a hazardous waste  landfill 	   5-81
 5-20     CQC  test location and  data summary 	   5-103
 5-21      Statistical analysis  of CQC test data  	   5-104
                                    xv

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                             FIGURES (continued)

Number                                                                  Page

 6-1      Location of past destructive earthquakes in the
          Uni ted States 	„..   6-12
 6-2      Differences in propagation of damage for eastern
          and western earthquakes 	„..   6-12

 7-1      Plan view of site A	   7-6
 7-2      Plan view of site B 	„..   7-8
 7-3      Plan view of site C	.....   7-10
 7-4      Cross-sectional  view of site C (vertical
          dimensions are to scale)	   7-12
 7-5      Plan view of site D	   7-15
 7-6      Cross-sectional  view of site D liner	   7-17
 7-7      Plan view of site E	.........:   7-19
 7-8      Cross-sectional  view of site F	   7-22
 7-9      Plan view of site G	   7-26
 7-10     Plan view of site H	   7-29
 7-11     Cross-sectional  view of site H liner showing
          details of leachate collection system and lysimeter
          constructi on	   7-30
 7-12     Plan view of site I	   7-36
 7-13     Cross section of liner at site I	   7-37
 7-14     Plan view of site J 	...   7-39
 7-15     Cross-sectional  view of site J liner	...   7-41
 7-16     Cross-sectional  view of site K liner	„..   7-43
 7-17     Cross section of containment system at  site L	„..   7-47
 7-18     Cross section of site M	„..   7-50
 7-19     Plan view of site M leachate collection and leak
          detection systems	   7-51
 7-20     Plan view of site N	   7-57
 7-21     Cross-sectional  view of site N liner and leachate
          management systems	   7-53
 7-22     Cross section of site P showing relationship of
          liner and dikes	   7-63
 7-23     Detailed cross section of site P  liner	   7-64
 7-24     Cross section of site Q liner	   7-69

 8-1      Flow domain for  leachate flow	   8-3
                                    xvn

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                                    TABLES
                                  • *"- '' '         Jg   L •:• .

No.                                                                     Page

2-1   Clay Mineral Characteristics	  2-5

3-1   Soil Tests Summarized  in Appendix A	  3-3
3-2   U.S. Standard Sieve Sizes and Their Corresponding
      Open Dimension	  3-13
3-3   Z/A of Various  Soil Components  	  3-30
3-4   Summary of Potential Errors  in  Laboratory
      Permeabi 1 ity Tests -on  Saturated Soi 1	  3-41
3-5   Summary of Sources of  Error  in  Estimating Field
      Permeability of Compacted Clay  Liners
      from Laboratory Tests  	  3-42
3-6   Test Results Showing Effect  of  Sample
      Diameter  on Permeability Measurements 	  3-45

4-1   Results of Permeability Tests With Organic Chemicals 	  4-17
4-2   Results of Permeability Tests With Wastes 	  4-24
4-3   Void Ratio and  Coefficient of Permeability
      Relationships for Calcium- and Sodium-
      Montmorillonite Permeated by Water and Naphtha 	  4-30
4-4   Summary of Soil Permeability With Soltrol C and Water 	  4-30
4-5   Permeabilities  Measured With Lacustrine Clay
      Exposed to Water and Waste Liquids 	  4-34
4-6   Properties of Soils Tested	  4-36
4-7   Classification  of Clay-Organic Solvent Systems
      According to Swell Properties	  4-37
4-8   Percent Swell for Clay Soils in Contact With
      Organic Liquids and Water	  4-38
4-9   Grain Size Distribution, Mineralogy, and Properties
      of the Four Clay Soils	  4-41.
4-10  Characteristics of Soils Used in Permeability Tests 	  4-56
4-11  Permeability Coefficients (cm/s) Determined
      in Soils Tested With Organic Solvents 	  4-57
4-12  Mean Conductivity of Each Soil  to Each Fluid   „
      Tested (Brown and Thomas, 1984)  	  4-71
4-13  Properties of Clay Soils Tested by Daniels and
      Liljestrand (1984)	  4-79
4-14  Leachate Characteristics 	  4-80
4-15  Permeability Test Results (Pennsylvania Case A)	  4-87
4-16  Permeability Test Results (Pennsylvania Case B) 	  4-88
4-17  Chemical  Characteristics of Waste Permeants, Project E 	  4-91
4-18  Results of Permeability Tests,  Project E 	  4-92
4-19  Results of Permeability Tests,  Project L 	  4-95
4-20  Initial and Final  Permeabilities Determined
      in Triaxial  Cell Tests With Leachates, Project N	  4-95
4-21  Effect of Concentrated Organics on a Treated
      Bentonite Seal   	  4-97
4-22  Permeability (cm/s) of a Treated Bentonite
      Seal  to Kerosene 	  4-97
                                    xvn

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                              TABLES (continued)
 No.
                                                                         Page

 5-1    Accessible Methods of Subsurface  Exploration	   5-7
 5-2    Nonaccessible Methods of Subsurface  Exploration	   5-9
 5-3    Properties of Soils Used To Construct  Soil  Liners	   5-11
 5-4    Properties of Soils Used To Construct  Soil  Liners	   5-112
 5-5    Factors  Controlling Stability of  Sloped  Cut
       in  Some  Problem Soils	„	   5-25
 5-6    Relative Volume Change of a Soil  as  Indicated
       by  Plasticity Index and Other Parameters	   5-36
 5-7    Soil  Volume Change as Indicated by Liquid Limit  and Grain
       Si ze	.	   s_36
 5-8    Effect of Clod Size on Permeability  of Laboratory
       Compacted Clay	„	   5.153
 5-9    Compaction Equipment and Related  Specifications  for
       Constructing Soil  Liners	   5-58
 5-10   Compaction Equipment and Methods	   5-63
 5-11   Current  QA Practices for Clay Liner  Construction	   5-99
 5-12   Recommendations for Construction  Documentation
       of  Clay-Lined Landfills by the Wisconsin Department
       of  Natural  Resources	   5-101
 5-13   Elements of a Construction Documentation Report	   5-102
 5-14   Potential  Clay Liner Design and Installation
       Problems and Preventive Measures	   5-110

 7-1    Clay-Lined Facility Information		   7-3
 7-2    General  Occurrence of Chemical Parameters in the
       Groundwater at Site C	   7-13
 7-3    Lysimeter (L)  and  Leachate Collection  System (LCS)
       Liquid Volumes (gal)  at Site H	   7_'(2
 7-4    Monitoring  Data for Site H	   7-34
 7-5    Heavy Metal  Content and Percent Solids of Lime
       Sludge Disposed at Site M	   7-Bi2
 7-6    Groundwater Monitoring  Well  Sample Analysis at
       Site M		o..   7.54
7-7    Leachate Analysis  at  Site  M  	.....!!!!   7-56
7-8    Leachate Volumes at Site M	   7-57
7-9   Water Sample Analysis:   BOD, COD, Total Coliform,
      and Fecal Coliform	  7.50

8-1   Comparison  of Transit Time Predictions	  8-15
                                    xviii

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                              ACKNOWLEDGMENTS


     The support of the U;S. Environmental  Protection Agency,  Cincinnati,
Ohio, and Dr. M. H. Roulier, EPA Project Monitor,  is greatly appreciated.

     The draft version of this document was prepared at the Research  Triangle
Institute by Dr. L. J. Goldman, Project Leader (currently with the  NUS
Corporation), along with Mr. R. S. Truesdale, Ms.  G. L. Kingsbury,  Ms.  C.  M,,
Northeim, and Mr. A. S. Damle.  This final  version was prepared by  the  NUS
Corporation by Dr. L. J. Goldman, Project Leader,  and Mr. L. I. Greenfeld.

     The authors wish to acknowledge the firms,  agencies, and  individuals
that provided much of the information contained  in this document.   We also
wish to acknowledge the contributions of those individuals who provided
reviews, comments, and suggestions on the draft  version of this TRD.
                                    xix

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                                   CHAPTER 1

                                 INTRODUCTION


      A clay liner consists of one or more layers of cohesive soil  that have
 been compacted to achieve a low permeability.  The purpose of a clay liner'in
 a waste management facility (landfill,  waste pile, or surface impoundment)  is
 to serve as a barrier between waste materials and the hydrogeologic  environ-
 ment by limiting seepage from the .facility and to provide  support  for over-
 lying components of the facility.

      A clay liner is usually constructed of native soil  that contains
 appreciable amounts of clay-sized particles;  in some  cases other materials
 such as bentonite,  are mixed with the soil  when it does  not contain  suffi-
 cient clay.  A clay liner may be overlain by one or more flexible  membrane
 liners and primary  and secondary leachate collection  (drain)  systems.
 Figure 1-1 illustrates one possible liner configuration  for a  surface
 impoundment.

      A compacted clay soil  liner, because of  its low  permeability  (hydraulic
 conductivity),  limits the steady-state  seepage  from a facility.  In waste
 management facilities the clay liner also is  designed to delay  the release  of
 leachate  for  the longest  possible time  (transit time)  and  to have  sufficient
 structural  stability to support  itself  and  other components  of  the facility
 that may  lie  above  it.   Clay liners are used  not only in waste management
 facilities but  also in  many other applications  such as water storage  and
 conveyance structures.

      Although clay  liners are  a  widely  used technology,  there is very  little
 information on  their performance in limiting  seepage  from  operating waste
 facilities.   [7.2.1;  7.3.2]*  Performance predictions  have been based
 primarily  on  results  from permeability  tests  conducted on  laboratory-
 compacted  soils.  Laboratory testing  has  provided a great  deal of data that
 demonstrate the  permeability (hydraulic  conductivity) that can be achieved
 with  various  soil materials  and  compaction methods and how various types of
 wastes  can  interact with  soil materials  to change this permeability.  Even
 though  it  is common  practice to  use  such  laboratory results to predict the
 field behavior of a  liner,  there are  few  field data that confirm the validity
 of laboratory-derived soil permeability values as a measure of field permea-
 bility.  There are some field data  showing that permeability and seepage
 rates for field-compacted clay soil   liners are much greater than for
 laboratory-compacted soils.  [2.3.2; 3.8.3.1]  Until more field data are
available on the performance of clay  liners constructed with the best current
*Numbers in brackets refer to relevant sections of this document.
                                     1-1

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                                            Cover Soil and/or
                                            Riprap
              Leachate Collection
              System
                                                       Foundation
Not to scale.
Bottom Liner-
Compacted Low
Permeability Soil
Component
                                                                         Top Liner-
                                                                         Synthetic Membrane

                                                                        Bottom Liner-
                                                                        Synthetic Membrane
                                                                        Component
                                    Figure 1-1. Cross section of an idealized clay liner system.

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technology, permeabilities of laboratory-compacted soils should be regarded
as a goal rather than an accurate estimate of the performance of field-
constructed clay liners.       « >&.         >ti. ,*

1.1  SCOPE

     The objective of this Technical Resource Document (TRD) 1s to provide,
in a single source, all of the available information on design, construction,
and performance of clay-lined waste management facilities.  The broad topics
covered are:  clay properties and characteristics, [2.0]; geotechnical testing
of soils [3.0]; the compatibility of clays and chemical wastes [4.0]; the
design, construction, and construction quality assurance of clay liners
[5.0];, potential failure mechanisms [6.0]; the performance of existing facil-
ities [7.0]; and methods of predicting the useful life (transit time) based
on the modeling of leachate flow through soils [8.0].  It should be noted
that the design and construction section [5.0] is limited to practices
currently in use by engineers.  Information on recommended practices is
available in guidance documents issued by the USEPA Office of Solid Waste,
Washington, D.C.

     One of the major sources of information for this document was a series
of in-depth interviews with over 30 design/construction engineers who have
hands-on experience with clay-lined facilities in all areas of the country.
Some of the material obtained in these interviews appears here, in print, for
the first time.  Opinions and preferences stated in this document, except
when referenced to published material, were obtained from these interviews
and do not necessarily represent the preferences of the authors or USEPA.

     This document contains some soils information taken from a Technical
Resource Document on flexible membrane liners,  Lining of Waste Impoundment
and Disposal Facilities (Haxo, 1983).  Other important sources of information
were the published literature, discussions with researchers, interviews with
personnel from waste management companies and industries, and contacts with
State and Federal  regulatory personnel.  Waste management companies and
regulatory agencies were the primary sources for the information contained in
Chapter 7, Clay Liner Performance.

1.2  SUMMARY OF CURRENT PRACTICES
                                                     *
     The following is a summary of major current practices in clay liner
construction that are believed to affect the permeability of the liner; other
aspects of earthwork (cut and fill  volumes, etc.) are not covered.  The
practices summarized are average or typical of a large number of the cases
observed by the authors at operating sites or in construction documentation.
Instances of better or poorer practices were also frequently encountered by
the authors.

1.2.1  Investigation of Site Conditions (Field)

     Site investigations are conducted before construction to identify and
investigate borrow areas for liner material.  The borrow area and the soils
that will underly the liner are investigated through borings, pits, and
trenches cut across the area.  In situ soil properties and groundwater condi-
tions are identified and taken into account in  the design to avoid structural
                                     1-3

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 problems such as hydraulic uplift (heaving) or settlement of the soil  under-
 lying the liner.  The foundation (soil) underlying the proposed facility site
 is evaluated for structural properties through laboratory tests on removed
 samples and in situ testing.  [5.1.1; 5.3.3.2.1]

 1-2.2  Material Selection and Characterization (Laboratory)

 1.2.2.1  Foundation Soil--
      Soil underlying the proposed facility must possess bearing and  shear
 strength adequate to support expected loading.  If tests on  samples  examined
 In the laboratory and onsite bearing tests show inadequate properties,  the
 site design and construction plans will include specifications  that  provide
 for excavation and recompaction of an adequate foundation.  [5.1.3-2.1;  6.2;
 6.3]

 1.2.2.2  Index Properties of Liner Materials--
      Samples of soils from potential borrow areas  are  analyzed  to  determine
 their index properties (grain size distribution, Atterberg limits, and
 Unified Soil Classification).  [3.3; 3.5.2; A-26;  A-28; A-29; A-34;  A-37]
 This information is used to identify and reject undesirable  materials  (i.e.
 low plasticity index or low fines content) and to  select desirable
 materials.

 1.2.2.3  Engineering Properties of Liner Material —
      A very important criterion for a suitable liner soil  is whether it  can
 be compacted so that the permeability (hydraulic conductivity),  as
 measured in the laboratory, is 10-'  cm/s or less.   A number  of  engineer-
 Ing firms and regulatory agencies have guidelines  for  the plasticity index
 and amount  of fines (amount passing  a No.  200  sieve) and some have acceptance
 criteria that consider only plasticity index or fines,  but,  at  present,
 permeability appears to be the most  heavily weighted criterion.      i

      Selection  of a liner material  that can be compacted to  the  required
 permeability involves a series of laboratory tests  of  the  engineering proper-
 ties of the candidate materials.  A  moisture content/density relationship is
 established for the material  by compacting samples  of  the  material at various
 moisture contents with a set  compactive effort.  [2.3.2;  3.4.1;  3.8.4.5;
 uf5^  1V47;  A~5°J  The °Pt1mum molding water content is the  water content at
 which  the maximum dry density is  achieved.   The permeability (hydraulic
 conductivity) of  a  sample of  the  soil  compacted with the  same compactive
 effort at a  water content slightly greater than optimum is measured.  [2.3.2;
 l2  1   -1   he  relat1onsfiip  between  density, moisture  content, compactive
 effort,  and  permeability derived  from  these  data will be used to develop
 construction specifications and,  for quality control of  the  construction
 process,  to  ensure  that  the water content  is slightly wetter than optimum and
 that compaction has  been  sufficient  to  achieve the desired permeability.
 * fu  ;,?*6; 5<1'4;  5.3.3.2.4]  It is  also necessary to construct a test fill
 of the  liner material  prior to construction to confirm that the laboratory-
 derived  relationship can  be achieved in the field.   [1.2.4; 5.2.2.1.4;
 5.3.3.1]

     In addition to meeting permeability requirements,  liner  material must be
compatible with the waste it is meant to contain.  A laboratory-compacted
sample of the son will be tested to determine  whether  wastes or leachates
                                     1-4

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from the proposed facility will react with it to increase its permeability
and decrease Its ability to control seepage from the facility.  [4.3; 4.4;
7.6.4]                .         ••?-  f   '     " =>

1.2.3  Develop Liner Design/Construction Plans

1.2.3.1  Lift and Liner Thickness—
     The depth of loose soil laid down for compaction (lift thickness) is
selected so that the equipment and operating conditions will be capable of
imparting the required compactive effort throughout the lift.  [5.2.2.1.1]
Minimum liner thickness is usually set by State or Federal regulations.
Beyond these minimums, liner thickness may be established on the basis of the
time required for liquid or waste to pass through the liner (transit or
containment time).  [5.1.3.3; 7.7; 8.0]  Greater than average liner thickness
may be specified at critical points such as the junction of the bottom and
side and below leachate collection lines or sumps.  [5.2.2.1.1]

1.2.3.2  Compactive Effort--
     Equipment and operating conditions (weight, number of passes, etc.) are
selected in conjunction with lift thickness to ensure that the same compac-
tive effort will be applied in the field as was used in the laboratory to
achieve the specified permeability.  [3.4; 5.2.2.1.4]  This selection will be
confirmed in the test fill.  [1.2.4]

1.2.3.3  Adjust Design to Avoid Failure Mechanisms—
     The design of the liner and the foundation (underlying soil) will be
adjusted to avoid common failure mechanisms, as appropriate:

     «    Erosion [5.1.3.4; 6.6.2]
     «    Freezing [5.1.3.4.3; 5.2.2.3.2; 6.7]
     •    Piping [5.1.3.4.4; 6.4.3]
     o    Slope instability [6.2]
     «    Settlement [6.3]
     «    Earthquake [5.1.3.4.6; 6.8]
     »    Scouring (surface impoundments) [5.1.3.4.2; 6.9]
     (i    Hydraulic uplift (heaving) [5.1.3.4.7; 7.4].

1.2.4  Pilot Construction Test (Test Fill)
                       — Him _-_.-!• i.-r-.i-j..-.jii-_-___ll___u.L	    ^ *i           —

     A small-scale construction test is conducted to determine whether the
selected combination of lift thickness, equipment, operational procedures,
moisture content, and density will result in the design permeability identi-
fied during the laboratory testing.  [5.2.2.1.4; 5.3.3.1]

1.2.5  Construction

1.2.5.1  Foundation Preparation—
     The native soil is the foundation for the clay liner.  The soil surface
will be, at a minimum, cleared, grubbed, stripped, and cleaned of organic or
otherwise deleterious material prior to placement of the liner material.
Resulting holes and depressions in the soil or underlying rock will be
filled.  Where necessary, the soil  may be excavated and recompacted using
standard earthmoving equipment.  Water content and compactive effort will be
                                     1-5

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 adjusted to give a firm surface for construction of the Uner.   The  surface
 may be proof-rolled to locate soft spots prior to placing liner material.
 [5.2.1.1; 5.3.3.2.1]

 1.2.5.2  Liner Material Preparation-
      Soil material for the liner will be either excavated on  site  or brought
 from a nearby borrow area.  Areas containing material  that is unsuitable
 because the fines content is too low or because it contains rocks, organic
 matter, etc., will be identified; material  from these  areas will be  segre-
 gated from the liner material and not used  in the liner.   [5.3.3.1;  7,5.1.2]

      If the material  is too dry or heterogeneous, construction  equipment will
 be used to mix 1t and the water content may be adjusted by addition  of water
 prior to placement.  Adequate curing time must be allowed to  enable  added
 water to uniformly penetrate all  the liner  material.   Stockpiles of  liner
 materials are often covered or seal-rolled  to retard drying or  erosion.
 [5.2.2.1]

 1.2.5.3  Material  Placement--
      Liner material will  be hauled to the site from a  stockpile or borrow
 area and spread to the specified  loose lift thickness  as  estimated with a
 shovel  blade or staff.  [5.2.2.1.1]  Rocks  and other foreign  material may be
 removed 1f apparent.   Clods that  are larger than  the 11ft thickness may be
 reduced 1n size with  a disc or harrow.  [5.2.2.1.2; 5.3.3.2.2]

      Water content of the soil  will  have been measured on samples from the
 emplaced material.  [3.6.2.2; A-6; A-7]  If water content 1s  less than speci-
 fied in the design, water will  be added by  spraying from  a truck or  large
 hose before the soil  is compacted.  Adequate curing time  must be allowed.  If
 the son  is too wet,  1t will  be allowed to  dry somewhat before compaction.
 [5.2.2.1.3;  5.3.3.2.3]

 1.2.5.4  Compaction—
      The  soil  Is compacted using  equipment  such as  sheepsfoot or rubber-tired
 rollers until  the  density of the  soil,  at the specified moisture content, has
 reached the  value  specified in  the design.   [5.2.2.1.4; 5.3.3.2.4]  During
 construction,  density may be measured  by direct methods such as the sand cone
 or  balloon  but is  more commonly measured with  a nuclear density gauge.
 [3.6.2.1;  5.3.3.2.4;  5.3.3.2.5; A-19;  A-20;  A-22]  Samples of soil  may be
 taken during  compaction  to determine  1f the  water content 1s close enough to
 the design value.   Alternatively,  a  nuclear  moisture gauge may be used.

     The  top  of a  11ft (layer of  soil)  may be  scarified with a harrow or
 other equipment so  that there will be an  adequate bond with the lift placed
 above 1t.  The  edges  of lifts are  often beveled or overlapped  to ensure
 complete  coverage.  [5.1.3.3; 5.2.2.1.1]

 1.2.5.5  Completion—
     Upon completion of the  liner, samples may be taken for laboratory perme-
ability measurements;  alternatively, field permeability measurements  may be
made on the completed  liner.
                                     1-6

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      The surface of the liner may be proof-rolled to seal it and prevent
 erosion and the liner may be covered with a protective layer of soil  to
 reduce desiccation cracking if there will be considerable time before the
 liner is placed in service or before a leachate collection system or flexible
 membrane liner is placed over the clay liner.  [5.1.3.4.5; 5.2.2.3.1; 6.1.3]

 1.3  ANALYSIS OF CURRENT PRACTICES

      The current practices discussed in this section are those that would bp
 most likely to .improve clay liner performance (lower permeability)  if they
 were changed.  Most of this analysis is based on laboratory studies of the
 behavior of compacted soils; few .field studies of the relationship  between
 construction practice and permeability have been conducted.

 1.3.1  Liner Material

      Changes in the amount of  fines  (material  passing a  No.  200  sieve)  in  a
 soil  strongly affect the relationship  between  compactive effort  and water
 content  and the maximum density  and  permeability that can be achieved.
 Consequently,  efforts  in the following areas are likely  to result in  a  liner
 with  a more uniform and lower  permeability:

         Identification  of  the  range  of soil properties in  the  borrow
        area
     «  Determination of the water content, compactive effort, density, and
        permeability relationships for all the major and significantly dif-
        ferent bodies of soil 1n the borrow area, and verifying these rela-
        tionships in a field-compacted test fill

     •  Sorting soils so that those delivered to the construction site do not
        have properties significantly different from the soils that were used
        in developing the construction specifications.

1.3.2  Clod Size

     One laboratory study has shown that, for the same water content and
compactive effort, permeability increased as the size of the clods
Increased.  The mechanism responsible has not been identified but it is
ass.umed to be nonuniform compaction, nonuniform moisture distribution, or
inadequate bonding between adjacent aggregates, leaving planes of weakness in
the soil sample and areas of higher permeability.
fn           to r??uce clod s1ze dur1"9 excavation and placement of the soil
for the liner would improve chances for achieving a lower permeability in
several ways:                                                        J

     •  A small clod is more likely to have a uniform water content;  the non-
        uniform water content of larger clods will  lead to differences in
        density and permeability after application  of the same compactive
        effort.

     •  At any given water content,  the material  could be compacted more
        uniformly  because the range  in clod sizes would be smaller.
                                    1-7

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     •  If water addition were necessary, the added water could be distrib-
        uted-.more evenly; shorter times would be required for water to move
        from the outside to the inside of smaller clods than of larger
        clods.

1.3.3  Water Content

     Laboratory studies using homogenized soil samples that have been ground
to pass a 2-mm sieve have demonstrated that as water content is increased
several percentage points above optimum, the permeability of the soil when
compacted decreases sharply.  Permeability may decrease by a factor of 100
over a water content range of only 2.0 to 4.0 percent above optimum.

     During construction, a uniform water content slightly higher than the
optimum for maximum density is likely to result in lower permeabilities than
would water contents that are optimum or less.  Considerable effort may be
required to control water content'under field conditions but all available
information indicates that a considerable return may be realized in terms of
lower permeability.

1.3.4  Pilot Construction (Test Fill)                                 '.

     There are a number of differences between laboratory and field condi-
tions  (uniformity of material, control of water content, compactive effort,
compaction equipment, etc.) that make it unlikely that permeabilities
measured on laboratory-compacted samples can be achieved during construc-
tion.  In addition, there are several processes and conditions"that cannot be
examined or anticipated through laboratory work (e.g., control of desiccation
cracking, bonding of lifts, degree of compaction on sidewalls),,  Pilot
construction (test fill) provides an opportunity to verify that the materi-
als, equipment, and personnel that will be used to construct the liner can
produce a liner that performs according to the design.  Specific factors that
can be examined/tested during construction of a test fill to increase the
probability of achieving minimum permeability in the actual clay liner are:

     •  Preparation and compaction of foundation material to the
        required bearing strength

     •  Methods of controlling uniformity of material, clod size, and water
        content

     •  Types of equipment and estimates of operational conditions (e.g.,
        number of passes).required to achieve design density, compactive
        effort, and permeability

     t  Lift thickness and placement procedures necessary to achieve uniform-
        ity of density throughout a lift and the absence of apparent boundary
        effects between lifts or between placements in the same lift

     t  Procedures for protecting against desiccation cracking or other site-
        and season-specific failure mechanisms for the finished liner or
        intermediate lifts
                                     1-8

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      •   Measuring  the  permeability  on  the  test  fill  in  the  field and collect-
         ing  samples  of field-compacted soil  for laboratory  testing

      •   Test procedures for  controlling the  quality  of  construction


                                    °f  S011 t0 meet Permeabi11ty requirements
      •   Skill and  competence  of  the construction team.

 1.4   SUMMARY


 nnnhaSlS  11ners.are a widely used technology for management of hazardous and
 nonhazardous wastes.  Field data on the performance of clay liners or on the
 ?-I?JV   yariouf  construction procedures on the permeability of liners are
 inn ted.   Laboratory data show that low permeabilities (less than
 lu    cm/s) can be  achieved by compacting soils.  The few case studies

 ™  *!!  been1conducted Su99est tnat permeabilities measured on laboratory-
 compacted  samples  or on small-diameter intact samples are poor predictors of
 performance of the actual liner.  A large body of information exists that

 like?v ?0W?InrnufP??nf °f C5nstruct1on Practice, if changed, would be most

  nMiTOZi^
                                           with values approaching
1.5  REFERENCE


Haxo, H. E. et al.  1983.  Lining of Waste Impoundment and Disposal
     Facilities.  SW-870, U.S. Environmental  Protection Agency, Cincinnati,
                                    1-9

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                                  CHAPTER 2

                                  CLAY SOIL


     Clay liners are composed of layers of cohesive soil, engineered and com-
pacted to form a barrier to liquid migration.  From an engineering stand-
point, soil has been defined as unconsolidated accumulations of solid
particles produced by the physical and chemical disintegration of rocks
(ASTM, 1985) or all materials in the surface layer of the Earth's crust that
are loose enough to be moved by a spade or shovel (Winterkorn and Fang,
1975).

     Soil may be viewed as a three-phase system composed of solids, liquids,
and gases.  The solid phase is composed of inorganic and organic particles of
varying shapes and sizes.  The liquid phase is usually an aqueous electrolyte
solution.  The gaseous phase is basically air with variations in composition
resulting from biological activity and chemical processes in the soil.  Soils
are normally characterized by.the size and composition of their solid (par-
ticulate) components, with air- and water-filled voids considered together as
porosity.  However, the relative amounts of air and water (usually expressed
as the degree of saturation) also influence soil behavior.

    The term clay can be defined in several ways.  Clay can refer to all  soil
particles less than a given size, usually 2 urn (Mitchell, 1976).  In soils,
this particle size range is composed of clay minerals and other components.
Clay minerals give a clay soil  its plastic and cohesive properties.  Other
components of the clay size fraction include nonclay minerals (e.g., marl  and
chalk), amorphous material, and organic material.

     Geotechnical engineers use the term clay to refer to soils that contain
enough clay size particles to affect their behavior CHoltz and Kovacs,
1981).  Because of its emphasis on the engineering properties of clay as  a
liner material, this document uses the term clay to refer to clay soil, with
clay mineral being used when referring to mineralogy and clay size being  used
when referring to particle size.

     This chapter discusses the characteristics of clay soils and the clay
minerals that are important soil constituents.  It is intended to give the
reader a brief overview of these materials, to present some basic defini-
tions, and to discuss the properties of clay soils and clay minerals that
influence the performance of clay liners.  The formation and occurrence of
low-permeability, clay-rich soils are also discussed.  For a more thorough
discussion of clay mineralogy or of the geotechnical  behavior of soil, the
reader is referred to Grim (1962, 1968), Mitchell (1976), and Perloff and
Baron (1976).
                                     2-1

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 2.1  CLAY MINERALS

      Clay minerals are hydrous silicates,  largely of  aluminum, magnesium, and
 iron, that, on heating, lose adsorbed and  constitutional water and yield
 refractory material at high temperatures.   Plasticity is characteristic of
 clay minerals and is largely due to an affinity of the clay  surface for
 water, resulting from a net negative charge on  the surface of a  clay particle
 that causes it to adsorb water and other polar  fluids. This net negative
 surface charge results from defects in the clay mineral crystal  structure and
 from surface chemical  reactions, as described below.   Because of their
 electrochemical  surface activity and high  surface area (resulting from their
 small size and lamellar shape), clay minerals can profoundly affect aisoil's
 engineering behavior,  even when present in small  quantities. As the clay
 content of a soil increases, the influence of the clay fraction  on its
 behavior also increases.  The strong influence  of clay minerals  on soil
 behavior can be  illustrated by the addition of  bentonite to  a granular soil.
 Bentonite 1s a clay material composed largely of the  clay mineral sodium
 montmorillonite.  An addition of only 2 to 3 weight percent  bentonite can
 reduce a soil's  permeability when it is compacted by  2 to 3  orders of
 magnitude (Kozicki and Heenan,  1983).  The influence  of clay minerals on a
 soil's behavior  increases with  increasing  clay  content to a  range of 33 to
 50  percent,  at which point the  nonclay size material  is essentially floating
 1n  a clay matrix and has little effect on  the engineering behavior of the
 soil  (Mitchell,  1976;  Holtz and Kovacs,  1981).

 2.1.1  Clay Mineral  Structure

      Most clay minerals have a  sheet-like  layered crystalline structure and
 thus  fall  Into the phyllosilicate mineral  family.  Exceptions are the clay
 minerals attapulgite,  palygorsite,  and sepiolite, which have structures com-
 posed of double  chains  of silica tetrahedra.  These minerals are not common
 1n  soils and  are not discussed  further in  this  document.

      Clay mineral  sheet structures  consist  of two different  layer types, one
 composed of  tetrahedral  units and  the other  of  octahedral  units, that are
 arranged 1n different  sequences  to  form  the  different  clay minerals.   The
 tetrahedral  unit 1s  composed of  silica tetrahedra in which four oxygens sur-
 round  a  silicon  atom in  tetrahedral  coordination  (Figure 2-1).  The octahe-
 dral  sheet, which  is made  up  of  cations  octahedrally'coordinated with oxygen
 (Figure  2-2),  occurs 1n  two  forms.   If the cation is trivalent,  only  two-
 thirds of the  possible  spaces in a  layer are filled and the structure Is
 dloctahedral.  The most  commonly occurring dioctahedral sheet in clay min-
 erals  1s the gibbsite sheet,  in which the cations are aluminum.   If the
 cation 1n the  octahedral  sheet is divalent, all  of the available cationic
 spaces are filled and the  structure  is termed trioctahedral.   The most
 commonly occurring trioctahedral sheet in clay minerals is  the brucite sheet,
 in which the cations are magnesium.

     Isomorphous substitution, or the substitution of different,  similar-size
cations for those present  in the ideal crystal  structure without a change in
structure, 1s  common in clay minerals and 1s an  important  factor in their
behavior.  Common cation  replacement  1n clay minerals  Includes aluminum
 (A1+3) for silicon (S1+4), magnesium  (Mg+2) for  aluminum (Al+3)}  and
ferrous iron   (Fe+z) for magnesium  (Mg+2) in the ideal tetrahedral and
                                     2-2

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              and
Oxygens
                                      Q and • " Silicons
                              Si
                                                       Si
                                          (c)
 (a) Silica tetrahedron.
 (b) Silica tetrahedral sheet.
 (c) Schematic of silica sheet. See Table 2-1.

Source: Lambe, 1958; Grim, 1968

                Figure 2-1. Clay mineral tetrahedral sheet structure.
              O and O * Hydroxyls or  £ Aluminums, magnesiums, etc.
                        oxygens
                             Al
                                                     Al
                                         (c)
        (a)  Octahedron.
        (b)  Octahedral sheet.
        (c)  Schematic of gibbsite octahedral sheet. See Table 2-1.

        Source:  Lambe, 1958; Grim, 1963

                Figure 2-2.  Clay mineral octahedral sheet structure.
                                        2-3

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octahedral sheets described above.  Isomorphous substitution in clay minerals
results in a charge deficiency in the crystal structure and a net negative
charge on the mineral's surface.

     The variety of cation substitutions, both in and between the crystalline
sheets, and the intergrowth of layers of different character results in the
diversity of actual clay minerals.  However, despite the large number of clay
minerals, only a few are important soil-forming constituents.  Table 2-1,
(from Mitchell, 1976) summarizes important chemical and physical
characteristics of the clay minerals that commonly occur in soils.

2.1.2  Clay Mineral Groups

     This section describes the basic structural makeup of common clay min-
eral groups.  Although each clay mineral has a definite "ideal" structure,
many naturally occurring clays are.complex and do not fit the ideal  formulas
described herein.  Mixed-layer clays can occur, with crystals containing
structural units of more than one clay mineral group.  In addition,  soils
composed of a single clay mineral or clay mineral group are relatively rare;
multimlneral soils are more commonly encountered in most areas.  In  a study
of 137 soils across the United States, more than one clay mineral occurred in
about 70 percent of them (Lambe and Martin, 1953-1957).  Therefore,  it is not
possible to predict soil behavior accurately by assuming that only one clay
mineral predominates through soil material.  For more information on clay
minerals and their complex natures, the reader is referred to Grim (1968) and
Van Olphen (1963).

     All clay minerals, except those with chain structure, may be roughly
categorized into four groups based on the height of the unit cell, the com-
position of the sheets, and the kind of intersheet bonding that forms the
layers of unit cells.  These groups are kaolinite, smectite, illite  (or
mica-like), and chlorite.  This grouping is convenient since members of the
same group have comparable engineering behavior (Mitchell, 1976).  The
following subsections describe these groups and the mineral characteristics
that are Important determinants of the engineering behavior of clay.

 2.1.2.1  ICaolinite Minerals--
     The basic structural unit (unit cell) of the kaoJInite group is a 1:1
arrangement of a silica tetrahedral sheet and an alumina (gibbsite)  octahe-
dral sheet (Figure 2-3).  In the tetrahedral sheet, the tips of the  silica
tetrahedra all point toward the center of the unit.  The oxygen atoms at the
tips of the tetrahedra are common with one of the planes of oxygens  in the
octahedral sheet and compose two-thirds of the octahedral oxygens.  The
remaining positions In this plane are occupied by hydroxyls that are located
directly below each hexagonal hole in the network formed by the bases of
the silica tetrahedral (Figure 2-3).  The kaolinite basal spacing
is 7.2 A*.

     Minerals 1n the kaolinite group are composed of stacks of the 1:1
structural units (unit cells) described above.  These unit cells are held
together by van der Waals forces and hydrogen bonding between the tetrahedral
sheets and the octahedral sheets of adjacent unit cells.  These bonds are
strong enough to preclude the introduction of water between the unit cells
and thus any Interlayer swelling.
                                     2-4

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                                            TABLE 2-1.   CLAY MINERAL  CHARACTERISTICS3
       Type
Subgroup and
 schematic''
Ml neral
Ideal  formula/unit cellc
       Cations
octahedral/tetrahedral
       1:1       Kaolinite       Kaolinite
                                 Halloysite
                                 (dehydrated)
                                 (hydrated)
                                     (OH)8

                                     {OH)8 Si4Al4Oio

                                     (OH)8
                                                             Al4/Si4

                                                             Al4/Si4
M
       2:1       Illite
                 Smecti te
                                 mite
                                     (KiH20)2(Si)8(A1,Mg,Fe)4>6 020(OH)4           (Al ,Mg,Fe)4.6/(Al,Si)8
                                 Vermiculite         (OH)4(Mg.Ca)x(Si8_x.Alx)(Mg.Fe)6 02o.YH20     {Mg,Fe)6/(Si,Al)8
                                                     x =  1-1.4, y = 8
                                 Montmorillbnite     (OH)4Si8(Al3.34.Mg.66)02o.nH2od

                                                                    Na.66
                                                                                  Al3.34Mg.66/Si8
       2:1:1     Chlorite
                                 Chlorite
                                     (OH)4(SiAl)8(Mg.Fe)6 02o(2:l layer)
                                     (MgAl)e(OH)i2 (interlayer)
                                                                     (2:1 layer)/(Si,A1)8
                                                             (Mg,Al)6 interlayer
       See notes at end of table.
                                                                                                   (continued)

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                                                                    TABLE 2-1  (continued)
INJ

0>
Mineral
Kaolinlte
Halloysite
(dehydrated)
(hydra ted)
Illite
Vermiculite
Montmorillonite
Chlorite
Isomorphous
substitution
Little
Little
Si always replaced
by some Al. Balanced
by K between layers
Al for Si; net
charge of 1 to
1.4/unit cell
Mg for Al ; net
charge always =
0.66-/unit cell
Al for Si (2: I/layer)
Al for Mg (interlayer)
Inter! ayer bond
0-OH
Hydrogen-strong
0-OH
Hydrogen-s.trong
K ions-strong
Weak
0-0;
Very weak
expanding lattice
0-OH
Hydrogen-strong
Basal
spacing
7.2A"
7.2J
10. 1A
M
10.5-14&
9. eft-complete
separation
14^
CECe
(meq/100g)
3-15
5-10
5-40
10-40
100-150
80-150
10-40
Specific
surface (m2/g)
10-20
35-70
65-100
40-80 primary
870 secondary
50-120 primary
700-840 secondary

Liquid
limit
(%)
30-110
35-55
50-70
60-120

100-900
44-47
Plastic
limit
<«)
25-40
30-45
47-60
35-60

50-100
36-40
Shrinkage Activity
Umi t plasticity Index
(%) % < 2pm
25-29 0.5 !
0.1-0.5
15-17 0.5-1

8.5-15 1-7

         aAfter Mitchell  (1976).

         bS indicates silica tetrahedral sheet.
          G indicates gibbsite  octahedral sheet.       *
          B indicates brucite octahedral sheet.
          K indicates potassium Ions.
          0 indicates water layer.

         cTwo formula units required per unit cell.

         dArrow indicates source of charge deficiency.   Equivalent fia listed as balancing cation.

         eCation exchange capacity.

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 (a)
                                                                   Oxygens

                                                               (OH) Hydroxyls

                                                                   Aluminums

                                                               • O Silicons
(b)
                                 10.1 A
                                                  \
{C)
                                Water Molecules

                                                                           7.2 A
(a)  Diagram of kaolinite structure.
(b)  Hydrated hailoysite.
(c)  Kaolinite or dehydrated hailoysite.
  G = Gibbsite sheet.
Source: Grim, 1963; Mitchell, 1976

                     Figure 2-3.  Kaolinite group minerals.
                                     2-7

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      2.1.2.1.1  Kaoli ni te—Kaoli ni te is the most common mineral in this group
and  consists -of stacks of  1:1 unit cells comprised of silica tetrahedral and
gibbsite  (Al) octahedral sheets.  The stacks generally range from 0.05 to
2 /jm 1n thickness and can  attain thicknesses up to 4,000 jum; the stacks can
range from 0.1 to 4  urn laterally.  The specific surface area of kaolinite is
on the order of 10 to 20 m2/g of dry clay.

      A small net negative  charge on kaolinite particles results in a cation
exchange  capacity of 3 to  15 meq/100 g.  This charge has been attributed to
a small amount of isomorphous substitution in the silica or gibbsite sheets,
replacement of exposed hydroxyl hydrogens by exchangeable cations, broken
bonds around particle edges, or diffuse charges resulting from the large
size  and  surface accessibility of 0~2 and OH" molecules (Mitchell, 1976;
Winterkorn and Fang, 1975).  The stacked crystal structure of kaolinite
results in a blocky  form for this clay mineral and a larger size and lower
surface-to-volume ratio than other clay minerals.  This low surface area,
combined with the relatively small'negative surface charge, results in
kaolinite being the  least  electrochemically active and least plastic clay
mineral.

      Because of the  blocky structure of kaolinite particles, crystal edges
of this mineral group comprise 10 to 20 percent of the total crystal area
(Theng, 1974) and therefore exert a stronger influence on the electro-:
chemical behavior of these minerals than do the crystal edges of smectites
or illites (crystal  edges  comprise 2 to 3 percent of total crystal area for
montmorillonite; Theng, 1974).  Broken bonds on these edges result in
unsatisfied valences that  can be satisfied by cation or anion adsorption.
However, unlike the  structurally generated negative charges on the platy
crystal surfaces, these charges are affected by the pH of the environment.
Evidence suggests that the edges are positively charged at low pH and
negatively charged at high pH.  This results in kaolinite having a low
cation exchange capacity at low pH and higher cation exchange capacity at
high  pH (see Section 2.3.1).  Kaolinite has a higher anion exchange capacity
than  most clay minerals.  This may result from the presence of replaceable "
hydroxyl ions on the outside of structural  sheets.  Kaolinite thus has the
ability to fix certain negative ions (Deer et al., 1966).

      Compared with other clay minerals, kaolinite has. a lower affinity for
water, has a lower dispersivity (see Section 2.3), and does not achieve as
low a permeability upon compaction.  On the other hand, because it is not as
electrochemically active,  its behavior may be less affected by chemicals
than  other clay minerals.  Thus, a kaolinitic clay liner may have a higher
permeability than liners composed of other clays, but the permeability of a
kaolinitic clay liner may not be as sensitive to changes in moisture content
or to chemical  attack.

     2.1.2.1.2  Ha Hoy site—Ha Hoy site is another kaolinite group mineral
that  1s a common soil constituent in some areas.  This mineral  occurs in two
forms:  a nonhydrated type with a structural  composition similar to Icaolin-
1te and a hydrated form with a single layer of water interposed between unit
                                     2-8

-------
 kaolinite  layers  (Figure 2-3).  This  layer increases the basal spacing to
 10.1 A,  compared  with 7.2 %  for nonhydrated halloysite and kaolinite.
 Partially  hvdrated  halloysite  (metahalloysite)-with basal spacing from
 7.4 to 7.9 A  can  also occur.  The  interlayer water molecules in hydrated
 halloysite are believed to be  in a rather flat hexagonal network linked
 to each  other and to adjacent halloysite layers by hydrogen bonding.

     The hydrated form of halloysite  occurs in cylindrical tubes of over-
 lapping  kaolinite sheets.  The outside diameters of the tubes range from 0.05
 to 0.20  ym, with  a  median value of 0.07 urn, and range in length from a fraction
 to several micrometers.  The specific surface area of halloysite ranges from
 35 to 70 m2/g (Mitchell, 1976).

     Because  of the interlayer water  sheet in hydrated halloysite, inter-
 calation (introduction between the unit cells) of chemicals can occur.  This
 also results  in a slightly higher cation exchange capacity for hydrated
 halloysite (5 to  40 meq/100 g) than for kaolinite (3 to 15 meq/100 g).
 Halloysite also may be more affected  by chemicals than kaolinite.

     The interlayer water in halloysite is easily removed during drying, and
 this dehydration  is irreversible.  Because of this phenomenon, soil engi-
 neering  tests on  air-dried samples can give different results than those
 performed  on  samples at the original  field moisture content.  For this
 reason,  it is especially important that laboratory tests on soils with
 appreciable halloysite content be carried out on samples at the original
 field moisture content (Holtz and Kovacs, 1981; Hilf, 1975).

 2.1.2.2  Illite Minerals—
     The illitic  clay minerals are also known as the mica-like clay minerals
 because  of their  structural  similarity to hydrous micas,  mites are com-
 posed of mica-like  three-layer sandwiches with an octahedral sheet between
 two silica tetrahedral  sheets (2:1 layers).  These "sandwich" layers are in
 turn bound together by fixed or exchangeable cations.  The specific mineral
 species  in this group are determined by differences in octahedral  sheet com-
 position and  the  type of interlayer cations.  Two minerals in this group
 common in  soils are illite and vermiculite.

     2.1.2.2.1  Illite—Illite is an important constituent of clay soils and
has been described by Mitchell  (1976)  as "perhaps the*most commonly occur-
 ring clay mineral  found in soils encountered in engineering practice."
 Illite has almost the same crystalline structure as muscovite mica.  This
structure  is comprised of a  silica-gibbsite-silica sandwich, with  the tips
of the silica tetrahedra p.ointing toward the octahedral  gibbsite  sheet and
the oxygens at the tips being common with the octahedral  sheet (Figure 2-4),,
Isomorphous substitution of  aluminum for silicon in the  tetrahedral  sheet
results in a negative charge at the surface of these layers.  This charge is
balanced by potassium,  cesium,  and ammonium ions between the 2:1  layers;
these  ions fit tightly in the 1.32-X-radius holes in the bases of  the
silica sheet and as a result are fixed in position and are not exchangeable,,
Illite differs from muscovite in having  less isomorphous substitution in  the
                                     2-9

-------
 tetrahedral  sheet, a  lower negative surface charge, and a lower amount of
 potassium  between the layers.  The stacking of illite layers is also more
 random,  and  mite occurs with a much smaller particle size than muscovite.

      In  terms  of properties  important to clay liner performance, illite lies
 between  kaolinite and the smectite clay minerals.  Although extensive iso-
 morphous substitution results in a net negative charge on the c'lay mineral
 surface, the fixed potassium cations balance the charges and strongly bond
 adjacent 2:1 sheets together.  As a result, illite has intermediate
 values for surface area  (65  to 100 m2/g), cation exhange capacity (10 to
 40 meq/100 g),  swelling  index, and activity.  It is also intermediate in
 its  reaction to chemicals.   Because of the strength of the interlayer
 potassium  bonding, the basal spacing of illite remains at 10 A* when it is
 exposed  to polar liquids (Mitchell, 1976).  The potassium ions effectively
 prevent  the  intercalation of water, organic liquids, and other cations (Deer
 et al.,  1966).

      2.1.2.2.2  Vermiculite—Vermiculite is a fairly common mineral in clay
 soils and  usually occurs with other clay minerals.  Vermiculite has a 2:1
 structure  with  a poorly organized octahedral sheet sandwiched between two
 silica tetrahedral sheets (Figure 2-4).  The octahedral  sheet contains iron
 and magnesium  ions.

     As  with illite,  isomorphous substitution of aluminum for silicon is
 extensive  in the tetrahedral sheet, resulting in a net negative charge on the
 crystal  surface.  This positive charge deficiency is larger than that of the
 smectite minerals (see Section 2.1.2.4) and is usually balanced by interlayer
 layers of  divalent cations and water.  This larger charge deficiency results
 1n Vermiculite  having  the highest cation exchange capacity of all  clay min-
 erals (Deer  et  al., 1966).   The most common interlayer cations in  vermiculite
 are magnesium and, to a lesser extent, calcium.

     The amount of water that is intercalated in vermiculite is less vari-
 able than  that  in smectite and usually is limited to two layers of water
molecules.   The interlayer spacing is therefore fairly constant for
 vermiculite  but varies to some extent depending on the cations present
 between  the  layers.  Vermiculites can absorb organic liquids between their
 layers but take up less than the smectite minerals (Deer et al.} 1966).
The primary  specific surface area for vermiculite ranges from 65 to
 100 mz/g.  This is within the range reported for montmorillonite and, as
with montmorillonlte, the secondary (interlayer) surface area can  reach
very high values (870 m2/g)  (Mitchell, 1976).

2.1.2.3  Chlorite Minerals—
     Chlorite minerals in clay soils are almost always found in association
with other clay minerals.  Chlorites are composed of 2:1 layers of silica
tetrahedral  sheets surrounding a gibbsite or brucite octahedral  sheet, with
another  octahedral  sheet between the 2:1 mica layers (Figure 2-5).  Chlorites
thus may be  termed 2:1:1 clay minerals.

     Chlorites can have Isomorphous substitution and may be missing a few of
the octahedral  sheets between the 2:1 layers.  This can  result in  some
swelling from water uptake between the layers.   Chlorites are less active
                                     2-10

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                 Oxygens. (OH) Hydroxyls,     Aluminum, (   ) Potassium

             O and • Silicons (One-Fourth Reolaced by Aluminums)

                                         (a)
\

/
 n
\ X
s
/ \

\ X
£
X \

- Water Molecule
10 to u A
(14 A as
shown)

            (b)

(a)  Diagram of illite structure
(b)  Illite schematic.
(c)  Vermiculite schematic

Source:  Mitchell, 1976
 (C)

G = Gibbsite sheet.
B = Brucite sheet.
                           Figure 2-4.  Illite clay minerals.
                                        2-11

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                                 T
(a)
   Gibbsite
   or brucite
                                  X 3.
                                                                                  S.
                            (b)
                                                                           Several
                                                                            water
                                                                            Layers
                                           1.4 nm
                                                                            Several
                                                                            Water
                                                                            Layers
                   1
J.
                                   nH20 layers and exchangeable cations
                   (~\ Oxygens   (OH) Hydroxyls   A Aluminum, iron, magnesium

                    O and  9 Silicon, occasionally aluminum


      (a) Schematic diagram  of chlorite.
      (b) Schematic diagram  of montmoriilonite.
      (c) Diagram of smectite structure.

                          Figure 2-5. Chlorite and smectite clay minerals.
                                               2-12

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 than  the  smectites,  have a  cation exchange capacity similar to illite (10 to
 40 meq/10 g),- and may  be similar to illite in engineering behavior.

 2.1.2.4   Smectite Minerals—
      The  smectite group of  clay minerals includes 2:1 minerals whose unit
 cell  is composed of  an octahedral sheet sandwiched between two silica tetra-
 hedral sheets.  The  bonding between these 2:1 layers is by van der Waals
 forces and cations that may be present to balance out structural charge
 deficiencies  in the  2:1 layer.  This bonding is weak, and, as a result,
 the layers are easily  separated by adsorption of water or other polar
 liquids.   Thus, the  interlayer spacing of smectites can vary from 9.6 A
 to complete separation, and this results in the high swelling behavior and
 high  activity of these clay minerals.

      The  smectite minerals may be divided into two groups, based on the com-
 position  of the octahedral  sheet. .The montmorillonites have a dioctahedral,
 aluminum-based (gibbsite) octahedral sheet; the saponites have a triocta-
 hedral magnesium-based (brucite) sheet.  Only montmorillonite is commonly
 found in  soils.  The saponites are relatively unimportant as soil constit-
 uents and are not discussed further in this document.

      2.1.2.4.1  Montmori11oni te—Montmori11oni te is a 2:1 clay mineral with  a
 dioctahedral  gibbsite  sheet sandwiched between two silica tetrahedral sheets
 (Figure 2-5).  Extensive substitution of magnesium and other cations for
 aluminum  and  aluminum  for silicon results in a charge deficiency of 0.5 to
 1.2 (usually  0.66) on  the unit cell (Mitchell, 1976).  Most of the substitu-
 tion  in montmorillonite occurs in the octahedral gibbsite sheet, usually one
 magnesium for every  sixth aluminum.  This results in a charge on the mineral
 surface that  is more diffuse or evenly spread than that of vermiculite, which
 has mostly substitution of aluminum for silicon in the outer, tetrahedral
 layers (Deer  et al., 1966; Winterkorn and Fang, 1975).   The charge defi-
 ciencies  on the montmorillonite unit cells are balanced by exchangeable
 cations between the  unit cells, and, as a result, montmorillonite exhibits a
 high  cation exchange capacity (generally 80 to 150 meq/100 g).

      The  bonding forces between unit cells of montmorillonite are weak, and
 water and polar fluids can easily penetrate between the unit cell layers. As
 a result, montmorillonite particles are very small and can be dispersed
 to sheets  of  unit cell thickness (10 8) in water (Mitchell, 1976).  The
 specific  surface area  of montmorillonite is very high, with a primary
 surface area  of 50 to  120 m2/g and a secondary surface area (including
 interlayer  surfaces) of 700 to 840 m2/g.  Because of its high specific
 surface and tendency to adsorb interlayer water, montmorillonite 1s very
 susceptible to swelling and is the most active of the clay minerals.
 Montmorillonite is especially sensitive to alteration by chemical attack.

      The  type of cations occupying the interlayer spaces strongly influ-
 ences the behavior of montmorillonite.  The most commonly occurring Inter-
 layer cation  1s calcium, a divalent cation.  Like vermiculite, caldum-
montmorlllonites usually take up two layers of water between the unit cell
 layers (Deer et al., 1966).  This results in limited swelling to a maxi-
mum interlayer spacing of 19 A* (Theng, 1974).  However,  when sodium 1s
                                    2-13

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 the interlayer cation,  as occurs in the Wyoming  bentonites  (see  2.1.2.4.2),
 the amount of interlayer water is not so limited and  the  interlayer  spac-
 ing can range" from 10 A (oven-dry)  to over  50  X  (Theng, 1974).   This
 results in high swelling, which is  characteristic of  sodium-montmori11onite;
 1t can expand to 13.8 times its dry volume  when  fully hydrated.

      2.1.2.4.2  Bentbnite—Bentonite is not a  clay mineral.   It  is a  rock
 (or clay deposit)  composed largely  of the clay mineral montmori'llonite.  The
 swelling and dispersive properties  of this  mineral give bentonite the ability
 to lower the permeability of a soil, even when added  in small quantities
 (e.g., 1 to 3 percent by weight).  The swelling  capacity  of bentonite depends
 on its sodium-montmorillonite content.  Low-swelling  bentonite has signifi-
 cant quantities of calcium-montmori11onite,  which, because of limited inter-
 layer water uptake,  does not swell  to the extent of sodium-montrnorillonite.
 High-swelling sodium bentonite has  a liquid limit of  500  percent or more and
 can swell  15 to 20 times in volume.   Calcium bentonite will increase  in
 volume 0 to 5 times  when wetted with water;  this swelling capacity has been
 reported to increase 700 to 1,000 percent by treating  calcium bentonites with
 a  0.25-percent solution  of ^003 (Fisher,  1965).

      Bentonite is  formed by the weathering  of  volcanic ash.   Environmental
 conditions favorable to  sodium bentonite  formation are semiarid  climate and
 alkaline soil  and  groundwater.  The  type  locality for  bentonite  is Wyoming,
 and most sodium bentonite comes from the  western United States and Canada
 (Hosterman, 1985).  Calcium or low-swelling  bentonite  is mainly  obtained from
 deposits in the Gulf Coastal  Plain  formed from weathering of  volcanic ash
 deposits (Hosterman, 1984).                                          i

 2.2  CLAY FORMATION  AND  OCCURRENCE

      This  section  presents some of  the factors that influence the formation
 and occurrence of  clay  soils  in the  United  States.  It is intended to help
 the reader comprehend the complexity of soil-forming processes and the degree
 of heterogeneity and variability that  may be expected  in naturally occurring
 soils  that may be  used for clay liners.   It  is not intended to be a complete
 treatise on the subject.

 2.2.1   Clay Mineral  Paragenesis
                                                     «
     Clay  minerals are products of weathering  or hydrothermal alteration,
 with different minerals  resulting from differences in physical-chemical
 conditions  and differences  in  parent material  (Deer et al., 1966).  Clay
 minerals may be found in  their place of origin or may be transported and
 deposited  in sediments.   In general, acid conditions favor the removal of
 cations  from the soil and  kaolinite  formation, and alkaline conditions favor
 the formation  of other clay minerals, with the predominant type(s) of cation
 Influencing  the clay mineral species.  A brief discussion of clay mineral
 formation follows.   A more  complete discussion may be found in Grim (1968),
 Keller  (1964),  and Weaver and  Pollard  (1973).

     Kaolinite mineral deposits are formed primarily by the weathering of
alkali feldspars and other silicate minerals common to sialic rock types such
as granites and quartz diorite.  Kaolinite occurs in residual, hydrothermal,
                                    2-14

-------
 and  sedimentary  deposits  (Patterson and Murray, 1984).  In the soil environ-
 ment,  acidic "conditions favor  kaolinite formation through the dissolution and
 removal  of  bases from  the parent material.  Kaolinite formation is favored
 where  alumina  is abundant and  silica  is scarce.  Kaolinites may be formed in
 situ but are usually a product of weathering and transport (Deer et al.,
 1966).   Kaolinite minerals may be found alone or in association with other
 clay minerals  in soils.  Kaolinite soils are prevalent in the southeastern
 United States, where they are  formed  from weathering, erosion, and redeposi-
 tion of  granitic material (Mason and  Berry, 1968) and in other humid regions
 with intense chemical  weathering and  good drainage.

     Illites are formed from the degradation of muscovite and from the
 alteration  of  other clay minerals.  The formation of illite is favored by
 alkaline conditions with high  concentrations of alumina and potassium (Deer
 et al.,  1966); illite  can be formed from smectites under these conditions.
 Illite is very common  in soils and. is almost always found in association with
 other  clay  minerals; its,stability is responsible for its abundance.

     Vermiculite in soils is formed from alteration of biotite, muscovite, or
 chlorite by weathering; it is  usually found in association with other clay
 minerals in soils.  Chlorite is also  commonly found in soils in association
 with other  clay  minerals; it may be formed from the alteration of other clay
 minerals (e.g.,  montmorillonite) in the presence of magnesia or by the
 degradation of ferro-magnesian minerals.  Alkaline environments rich in iron
 and  magnesium  favor its formation.

     In  general,  the formation of smectites is favored by alkaline conditions
 and  the  presence of calcium and magnesium.  However, smectites occur in
 association with illite in the prairie soils of the Midwest (pH 4.5 to 5).
 Calcium  is  usually the dominant exchange cation in smectites, except for
 deposits in the  western United States, where high-sodium-montmorillonite-
 content  (sodium  bentonite) clay deposits are formed from the alteration of
 volcanic rocks.   Montmorillonite is also found in soils formed by the
 weathering  of basic igneous rocks; poor drainage conditions promote the
 formation of montmorillonite in soils because magnesium is not removed during
 weathering  (Deer et al., 1966).  High calcium and magnesium and low potassium
 and  sodium  are also favorable  to montmorillonite formation, as are semiarid
 and  arid climates (Mitchell, 1976).                  -

 2.2.2  Clay Soil  Formation and Occurrence

     Clay soils  occur  throughout the United States in a variety of deposi-
 tional environments.   The characteristics of a clay soil  are influenced by
 the  parent  material of the soil and the soil-forming processes (e.g.,
 weathering, deposition).  Clay soil  may occur as transported soil  or residual
 soil.  Transported clay soil includes soil laid down by water action (fluvial
 soil) and soil deposited by ice action (glacial  deposits).  Residual  soil  is
 soil that is chemically weathered in place from the parent bedrock (USDI,
 1974).   Each of  these  soil-forming processes results in soils with different:
 characteristics.  The  processes involved in soil  formation are diverse and
multivariate, resulting in a wide range of chemical  and physical  variations.
                                    2-15

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 2.2.2.1  Fluvial Soils—
      Fine-grained, high-clay-content soils are found in the outer edges  of
 torrential outwash deposits or alluvial  fans (deposits laid down where an
 abrupt flattening of stream gradient occurs), especially in humid climates.
 Other alluvial (steam laid) deposits can also have high clay contents; sedi-
 ments from older, slow-moving, meandering streams have a larger fraction of
 fine-grained components (USDI, 1974).  Overbank,  floodplain deposits  laid
 down in still waters also tend to be fine-grained.

      Individual  strata of alluvial  deposits can vary considerably,  both
 vertically and horizontally and in  clay content and permeability (Freeze
 and Cherry, 1979).  A predominantly fine-grained  floodplain or  valley-fill
 deposit should be expected to have  many lenses or strata of coarse-grained,
 permeable material.   Complex vertical and lateral  facies changes,  from fine-
 grained overbank deposits to coarse-grained river channel  deposits, are
 common in valley-fill  and valley terrace deposits.  These lateral  facies
 changes result from  changes in a river course and changes in a  flow regime
 and reflect past and present geomorphic  processes and  environments.   Meander-
 Ing stream deposits  are especially  variable in this regard because  of the
 continuous changes in  river course  common to this geomorphic environment.
 Thus,  there is much  heterogeneity in alluvial  sediments  resulting  from
 textural  variability.   Hydraulic conductivities can vary more than  2  or  3
 orders of magnitude  in these deposits (Freeze and Cherry,  1979).   Because of
 this heterogeneity,  knowledge of fluvial  processes can  be very  helpful when
 site investigations  are conducted in areas  of alluvial  soils.   Alluvial
 deposits  are found in  river valleys  across  the United States, in glaciated
 regions,  and in  the  large intermountain  basins of the Southwest (Heath,
 1984).                                                                \

      Lacustrine  deposits are deposited by the still  water of lakes.   They
 are fine-grained,  finely stratified  deposits  with  low permeability, high
 compressibility,  and low shear strength.   Lacustrine deposits have flat
 surfaces  and are  surrounded by high  ground  (USDI,  1974).   Near  the edges of
 lake deposits, alluvial  influences  can result in  lenses  of coarse-grained,
 permeable material being interstratified  with the  fine-grained  lake sedi-
 ments.  As with  the  valley-fill  deposits,  these heterogeneities can result
 in  rapid  groundwater migration through the  permeable layers.  Lacustrine
 deposits  are common  in  glaciated regions, along the  Gulf  Coastal Plain, and
 1n  the  Intermountain basins of the West  (Freeze and  Cherry,  1979).

     Because they  are  laid  down  in still  or  slow-moving water,  fine-grained,
 low-permeability fluvial  deposits tend to have  a dispersed  soil  fabric (see
 Section 2.4.1  for  a  discussion of fabric).  However, flocculated fabrics also
 can  result  from fluvial  deposition.   Fluvial  soils  tend to  be anisotropic
with respect to permeability from stratification,  with permeability greater
 1n  the horizontal  than  in the  vertical direction.    In one  study of alluvial
and  lacustrine sediments  (Johnson and  Morris,  1962), 46 samples  had a greater
horizontal  than vertical  hydraulic conductivity, 11  samples were isotropic,
and 4 samples had greater vertical conductivities.   Horizontal conductivities
were 2 to  10  times larger than vertical conductivities in this study.
                                    2-16

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  2.2.2.2   Glacial  Soils--
      Glacial deposits  are  those,that are  laid down by the advances and
 retreats  of  the  North  American  continental  ice sheets and by smaller mountain
 glaciers  in  the  Rocky  Mountains,  the Sierra Nevadas, and Alaska.  Glacial
 soils tend to  be very  heterogeneous because the source material of a single
 soil  can  extend  over hundreds of  miles.   Deposits of the glacier proper are
 referred  to  as glacial-till  or  morainal deposits and are heterogeneous, well-
 graded deposits  with particle sizes ranging from clay to large boulders.
 They  are  deposited directly  from  glacial  ice with little or no sorting by
 moving water.  The rock  fragments are generally contained in a matrix of fine
 silt  and  clay, resulting in  a low-permeability soil with considerable shear
 strength.  These are excellent  qualities  for landfill sites and clay liner
 material.  For these deposits,  the fine clay material can have a flocculated,
 random fabric  because  till is deposited in mass from the wasting ice.  Fine-
 grained glaciofluvial  and  glaciolacustrine deposits tend to have a dispersed
 fabric because these deposits are fluvial in origin (see preceding discussion
 on fluvial soils).  However, flocculated  fabrics can result from fluvial
 deposition.

      The  heterogeneities common in glacial soils make a detailed site survey
 necessary  during investigations of a landfill site or borrow pit in glacially
 deposited  soils.   Field  permeability tests should be part of any site sur-
 veys  in glacial  soils  because of  the potential  for fractures and stratified
 heterogeneities.   Knowledge  of glacial processes is very helpful in delineat-
 ing heterogeneities during a site investigation in glacial  soils.

 2.2.2.3  Residual  Soils-
      Residual  soils result from the in situ weathering of underlying bedrock
 and are always present in  the place where they have formed.  The character of
 a residual soil  is determined by  the parent bedrock and the type and
 degree of weathering to which it  has been subjected (USDI,  1974).  Residual
 soils  are  rare in  glaciated  regions because the action of ice removed such
 soils  during the last glaciation, and not enough time has passed since then
 (10,000-12,000 years)  for weathering processes to form new soils from rocks
 in place.  Residual soils generally occur where transported soils or surfi-
 cial  bedrock are absent  (USDI,  1974).

      The mineralogy and physical  grain morphology for- residual  soils are
 different  from those of other soils.  Residual  soils are more leached than
 glacial or fluvial  soils, with  lower lime, magnesium, and potash contents and
 higher silica, alumina, and  iron-oxide contents.  Individual  mineral grains
 in residual soils  tend to be more rounded and weathered (decomposed) than in
 other  soils.  The  fabric of  residual soils can be flocculated,  or randomly
 oriented, as the mineral  grains are formed in place and not deposited with
preferential  orientation as are fluvial  soils.   However, weathering processes
 can also result  in dispersed fabric, depending  on the mineralogy of the soil
and the geochemical environment (see Section 2.4.1.1).

     Although most soils have unique compaction curves,  for a residual  soil.,
compaction curves at a given compactive effort  can change,  depending on the
soil  moisture content at the start of the test.  This has been  attributed to
the presence of halloysite (which exhibits irreversible  drying) and to
particle breakdown  during air drying and subsequent compaction  (HiIf,  1975),
                                    2-17

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 Irreversible changes during drying can  also  occur  for other  soil types  (see
 Section 3.8.3.1;  Sangrey et al.  1976).

 2.3  CLAY CHEMISTRY

 2.3.1  Electrical  Double-Layer Theory                                ;

      Most clay mineral  particles fall into the  size  range that defines  col-
 loids.   Colloids  are particles that are sufficiently small to allow inter-
 facial  forces to  be significant  in their behavior.   For clay minerals in
 soil  environments,  these interfacial  forces  are present as a charged solid-
 solution interface  that gives rise to an electrical  or diffuse double layer.

      An electrical  double layer  is composed  of  a layer of charges fixed on or
 within  the surface  of a solid and a layer of mobile  ions of  opposite charge,
 or counter ions,  distributed in  the liquid adjacent  to the surface.  These
 counter ions are  weakly held close to the surface  by electrostatic forces and
 can be  displaced  with respect to the charged, solid  surface  with movement of
 the liquid.

      The theory of  the  diffuse double layer  was originally developed by Gouy
 (1910)  and Chapman  (1913),  with  later modifications  by Stern (1924) and
 others, to explain  colloid  behavior.  Parks  (1975) and Stumm and Morgan
 (1970)  describe several  models of the double layer.  A simple model is
 illustrated in Figure 2-6.   In this case, electrostatic attraction between
 the adsorbent (negatively charged clay  surface) and  adsorbate (positive ions
 in solution)  results in a layer  of cations at the  surface (the Stern layer)
 and a diffuse layer of  cations in solution (the Gouy layer).  The cation
 concentration in  the Gouy layer  decreases with  distance from the negatively
 charged surface.  The thickness  of the  Stern layer is fixed  by the hydrated
 radius  of the adsorbed  counter ions;  the plane  through the center of the
 Stern layer counter ions is known as  the Stern  plane (Figure  2-6,
 diagram A).   The  thickness  of the Gouy  layer is defined as the distance from
 the charged  surface at  which the cation  and  anion concentrations reach that
 of the  bulk  solution.   From this point,  for  a negatively charged surface,
 cation  concentrations increase and anion concentrations decrease as one moves
 toward  the surface  (Figure  2-6,  diagram  B).
                                                     «
      The negative surface charge that generates the  electric double layer
 around  clay minerals may be attributed to two causes (Stumm and Morgan,
 1970):   (1)  imperfections or substitutions in the crystal  lattice of the clay
minerals (I.e., isomorphous substitution) and (2) charge deficiencies arising
 from  chemical  reactions  at  the mineral surface.  These surface chemical
 reactions  include those  involving  broken bonds at particle edges and non-
 cleavage surfaces and the interactions of potential-determining ions (H+
or  OH~), with  hydroxyl groups at  the exposed surface of the clay parti-
cle.  Isomorphous substitution is  the major  cause of negative surface charge
for all   clay minerals except perhaps the kaolinite group.   Surface chemical
reactions  contribute about  20 percent of the surface charge for smectites and
may be  the major source  of  surface charge for kaolinites (Mitchell,  1976).

     Negative  surface charge from  structural  causes is  not affected  by the pH
of the  solution surrounding the  surface  in question.  However,  charges aris-
ing from surface chemical reactions are directly affected  by solution  pH.
                                    2-18

-------
A.
                           Solid Surface
                            Stern Plane
                                           Solution
                            Gouy layer, charge = 0G incl. charge
                              in Stern plane
                             • Surface Charge = Oa
      Concentration
           of
B.    Counter- and
      Co-Ions in the
      Double Layer
— Concentration
  in Solution
                                  Distance from Surfaffe


             After Parks, 1975.


                    Figure 2-6. Electrical double layer.
                              2-19

-------
 Decreasing pH lessens the negative surface charge.   For a  given  solution
 and clay mineral, there is a characteristic pH,  the  pHpzc,  at which  the
 surface charge is zero.  At pH values lower than pHpzc,  the surface
 becomes positive and thus can act as an anion  exchanger (Stumm and
 Morgan, 1970).

      Figure 2-7 compares the effect of solution  pH on  surface charge,  in
 terms of electrophoretic mobility (EPM),  for kaolinite and  fuller's  earth, a
 clay material usually composed principally of  calcium  montmorillonite.  One
 may see that kaolinite is strongly affected by solution  pH,  with  fuller's
 earth being much less affected.  This supports the contention that most of
 the surface charge for kaolinite is due to surface chemical  effects.   Most of
 the total  surface charge of the 2:1 minerals (e.g.,  montmorillonite) results
 from defects in the crystal  structure inside the minerals and therefore is
 less affected by changes in pH.

      The thickness of the double layer of clay minerals  results  from a
 balance between the electrostatic attraction force holding  the diffuse cation
 layer to the surface of the mineral  and osmotic  forces tending to diffuse
 cations away from the mineral  surface.  The electrostatic attraction force
 depends on the mineral  properties (i.e.,  surface charge), while  the osmotic
 forces depend upon the properties of the  solution (including dissolved ions)
 surrounding the clay mineral.

      A more detailed discussion of these  effects may be  found in Mitchell
 (1976)  and in Chapter 4 of this document,  which  discusses the different
 effects of chemicals on clay permeability.   Quantitative treatment of  the
 electrical  double layer also is discussed  in Chapter 4.  However, it is dif-
 ficult to  apply the electrical  double  layer equations  to predict the behavior
 of  clay soils because of the complexity of the system.  Clay soils are almost
 always  composed of a variety of clay minerals, each  with different double
 layer characteristics.

 2.3.2   Cation-Exchange Capacity and Cation  Affinity

      The cation-exchange  capacity (CEC) of  a clay mineral may be defined
 as  the  excess  of  cations  in  the electrical  double layer that can be ex-
 changed  for  other cations  in the  bulk  solution (i.e.,  the shaded area in
 Figure 2-6b).   The  three-layer  (2:1) clay minerals exhibit the largest
 exchange capacities.  Typical CEC  ranges for clay minerals are presented in
Table 2-1.   Ranges  in CEC  result  from  variations  in  composition and environ-
mental factors; a given  clay mineral does not have a single CEC value
 (Mitchell, 1976).   It should also be noted  that  because clay soils are rarely
composed of  a  single  clay mineral and  because other nonclay substances (e.g.,
sand and rock  flour)  usually constitute a significant portion of the soil
mass, the cation  exchange  capacities of bulk soils are lower than those of
pure clay minerals.

     Cations differ  in  their probability of being adsorbed by a colloid.
There is a well-defined affinity  series of cations for clay mineral  sur-
faces.  For  cation-exchange equilibria dominated by electrical  clipole
                                    2-20

-------
       1O
   I   0.5
f  I    o
--J,
   1  -CL5)-
                                                   10  11   12— pH
                                                          for filler's earth
Source: Stumm and Morgan, 1970
  Figure 2-7.  Effect of solution pH on clay mineral su/face charge (EPM).
                                  2-21

-------
Interactions between the cations and water molecules,  the following  affinity
series exist:                            :                             :
and
                            Cs+ > K+  > Na+
                      Ba++ > Sr++ > Ca++ > Mg++ > Be
Thus, affinity increases with decreasing ionic radius for a given cation
valence.  This series does not apply to ion exchange sites that have affini-
ties for specific cations (e.g., interlayer illite potassium sites).

     As predicted by double layer theory, clay minerals have a greater affin-
ity for bivalent cations than for monovalent cations and this selectivity
decreases with increasing solution.ionic strength (Stumm and Morgan, 1970).
In addition, the selectivity of clay surfaces for different ions in  a mixed
ion system is temperature-dependent.  Mass action effects (i.e., high con-
centrations of specific cations in solution) can override the affinity series
(Mitchell, 1976).

     Cation exchange affects the double layer thickness and this, in turn,
can affect the permeability of clay soil through its effects on particle
arrangements.  Replacement of a monovalent cation by a divalent cation
results in a reduction in double layer thickness, lower interparticle repul-
sion and dispersion, increased flocculation, and increased permeability (see
Section 2.4.2).  This phenomenon is discussed in Chapter 4.  The properties
of clay minerals with higher cation exchange capacities (e.g., montmoril-
lonite) are more affected by cation exchange than those of clay minerals  with
low cation exchange capacities (e.g., kaolinite).  Cation exchange capacity
increases with increasing mineral surface area and surface charge.

 2.3.3  Significance of the Electrical Double Layer to Clay Liners

     The thickness of the electrical double layer is an extremely important
determinant of the engineering properties of a clay soil.  For clay  soils,
increasing clay mineral electrical double layer thickness results in a more
dispersed fabric and lower hydraulic conductivity (see Section 2.3).  Reduc-
tion in electrical double layer thickness for clay minerals can occur through
desiccation, cation exchange, and interactions with certain chemicals (see
Chapter 4 for further discussion of clay/chemical interactions)„  Reduction
in double-layer thickness results in a more flocculated soil structure and
increased permeability.  Ttie effect of double-layer thickness in a clay soil
on its behavior also depends on the size and specific surface area of the
clay particles in the soil.  The behavior of smaller clay minerals,  with
higher specific surface area and surface charge (e.g., smectites), is more
affected by changes in double-layer thickness than clay minerals with lower
specific surface areas (e.g., kaolinite).  Relative sizes of clay minerals
are illustrated in Figure 2-8.
                                    2-22

-------
(a)
       Adsorbed water
                                               Kaolinite crystal
                                               (1000 X 100 nm)
               Montmoriilonite
               crystal
               (100 X 1 nm)
          Edge View
                               Typical
                              Thickness
                                (nm)
               Typical
               Diameter
                (nm)
Specific
Surface
(knv>/kg)
        Montmoriilonite
                                             100-1000
                                                               0.8
(b)
             Illite
                                30
                 10000
  0.08
           Chlorite
           Kaolinite
                                 30
                 10000
50-2000        300-4000
  0.08
                                                              0.015
   (a) Relative sizes of hydrated kaolinite and montmorillonite crystals.
   (b) Relative sizes of clay minerals.

   Source:  Lambe, 1958

             Figure 2-8.  Comparisons of clay mineral sizes
                            and surface areas.
                               2-23

-------
 2.4 CLAY SOIL FABRIC AND HYDRAULIC CONDUCTIVITY

     This section briefly discusses the fabric of fine-grained soils and the
engineering property of soils most relevant to clay liners; i.e., the rela-
tionship of compaction to hydraulic conductivity (permeability).  For more
information on these subjects, see Grim (1962, 1968), Mitchell (1976), and
Hilf (1975).  A discussion of clay/chemical compatibility, including the
effects of chemicals on soil hydraulic conductivity, may be found in
Chapter 4 of this document.

 2.4.1  Soil Porosity and Hydraulic Conductivity

     Porosity and hydraulic (or fluid) conductivity are two fundamental  soil
properties from the standpoint of fluid transport.  The pore size of a soil
is the most important factor influencing the soil's hydraulic conductivity.
Although a statistical relationship exists between porosity and hydraulic
conductivity for relatively uniform porous media (increasing porosity
increases hydraulic conductivity), it is difficult to relate, quantitatively,
porosity and hydraulic conductivity for clay soils (Mitchell, 1976).  How-
ever, this relationship can be discussed qualitatively.

     The physical structure* of a soil determines its porosity and its
hydraulic conductivity.  Two types of porosity may be delineated in soils:
primary and secondary.  These types of porosity are controlled by, respec-
tively, the microstructure (fabric) and macrostructure of the soil, as
described below.  In addition to primary and secondary porosity, macro-
structural heterogeneities (e.g., sand lenses and sand seams) also influence
the hydraulic conductivity of a soil mass.

 2.4.1.1  Soil Microstructure and Primary Porosity--
     Primary porosity is the porosity of the soil mass or soil matrix and is
controlled by the microstructure or fabric of the soil, which is influenced
by the particle size distribution and the arrangement of mineral grains.
Soils with a significant percentage of fine materials usually have low
hydraulic conductivities.  Most often this fine-grained material is composed
of clay minerals.  Some soils have low permeabilities- with only a small
percentage of fines as in the case of admixtures containing bentonite.
                                                    *
     Clay minerals generally have flat, platy particle shapes.  The orienta-
tion of the clay platelets in the soil is one of the most important param-
eters determining effective porosity and hence hydraulic conductivity in
fine-grained soils (Mitchell, 1976).  Moreover, the primary cause of micro-
scale anisotropy in fine-grained soils is the orientation of clay particles
1n a dispersed manner (Freeze and Cherry, 1979).  Figure 2-9 illustrates some
simple soil  fabrics that can occur in clay soils.  These are simplified
pictures.  Much more complicated particle arrangements usually occur, and a
single soil  may have many different zones of fabric.
     *Herein, structure refers to the physical  arrangement of the soil
constituents.                                                        :
                                   2-24

-------
                                                                        b.

(a)  Flocculated clay platelets.
(b)  Dispersed clay platelets.
(c)  Flocculated clay platelet groups.
(d)  Dispersed clay platelet groups.

Source:  From Holtz and Kovacs, 1981
                                                                       d.
                            Figure 2-9.  Clay soil fabrics.
                                       2-25

-------
      In fine-grained, clayey soils, fabric can refer to the arrangement of
 Individual clay platelets  (Figure 2-9, diagrams a and b) or to the    !
 arrangement of oriented groups of platelets (Figure 2-9, diagrams c and d)
 and the relationship of these platelets to larger mineral grains (silt and
 sand).  A soil's fabric helps determine its pore size.  In a flocculated
 soil  structure (Figure 2-9, diagrams a and c), the clay platelets or
 platelet groups tend to be edge-to-face oriented.  Soils with this fabric
 can be expected to have a  larger pore matrix with hydraulic conductivity
 that  is fairly equal in all directions.  In a dispersed soil structure
 (Figure 2-9, diagrams b and d), clay platelets or platelet groups tend to be
 oriented face to face, resulting in a deposit that is stratified on the
 microscale.  A dispersed soil structure will be anisotropic with respect to
 hydraulic conductivity with higher matrix hydraulic conductivity in the
 horizontal direction (parallel to the oriented clay particles) than in the
 vertical direction (perpendicular to the oriented clay particles) (Mitchell,
 1976).  The pore size of a dispersed soil structure is smaller than that of
 a flocculated structure.                                              ;

      Hydraulic conductivities in soils with dispersed fabrics tend to be
 lower than the hydraulic conductivities of similar soils with flocculated
 structures.  This phenomenon may be responsible for the difference between
 the measured hydraulic conductivity of a clay compacted wet of optimum
 and the hydraulic conductivity of the same clay compacted dry of optimum.
 Although equal density can be achieved in both cases, the hydraulic conduc-
 tivity of the soil compacted wet of optimum will  be less (vertical  direction)
 than  that of the soil compacted dry of optimum.  This difference in hydraulic
 conductivity can approach 2 orders of magnitude (Lambe and Whitman, 1979)
 and can be attributed to the increased dispersion of clay platelets and the
 resulting smaller pores when a soil is compacted at the higher moisture con-
 tent  (Daniel, 1984).  Mercury porosimetry data, reported by Acar and Seals
 (1984) for kaolinite compacted to the same dry density, wet and dry of opti-
mum,  suggest that higher hydraulic conductivities in dry of optimum samples
 result from a bimodal pore size distribution; although the cumulative poros-
 ity of the two samples is the same, the dry of optimum sample has both large
 (~ 25 urn) and small (~ 5 x 10~2 /am) pore sizes, whereas the wet of optimum
 sample has only the small pore size.                             .         	

      The fabric of an in situ clay soil is largely determined by soll-
 formlng processes responsible for its formation,  its depositional environ-
ment, and the action of postdepositional processes.  A very important factor
 influencing a clay soil fabric is the electrochemical environment at the
 time  of its deposition, including the mineralogy of the clay and the electro-
 chemical properties of the depositional medium.  These factors Influence the
thickness of the electrical double layer surrounding the clay particles (see
Section 2.3 for a discussion of double-layer theory).  Increasing the double-
 layer thickness increases the dispersivity of clay particles, thus decreasing
their tendency to flocculate during deposition.  Dispersed soil  fabrics tend
to occur when a clay with exchangeable sodium 1s  deposited in water with a
 relatively low electrolyte level  (Rogowski  and Richie, 1984).  In addition,
dispersed, anisotropic fabric may be developed in isotropic soils from post-
depositional  shear or compressive forces (Mitchell, 1976).  Flocculated
fabric can be created in virtually all  depositional environments (Holtz and
Kovacs, 1981) and can result from postdepbsitional  changes in the soil
environment (e.g., cation exchange).
                                    2-26

-------
  2.4.1.2   Soil  Macrostructure  and  Secondary  Porosity-
      Secondary  porosity  is  controlled by  the macrostructure of the soil and
 encompasses  the heterogeneities.ofssoil deposits  including joints, fissures,
 root  and  animal  holes, and  other defects  in  the soil mass (Holtz and Kovacs,
 1981).  Joints,  fissures, and/or holes can occur  in any soil as a result of
 stresses  on  the soil  (i.e.,  earthquakes,  slumping, and compression), desicca-
 tion, dissolution,  or the action of vegetation or animals.  In compacted
 engineered soils, secondary  porosity can  result from poor quality control of
 the compaction  process or from desiccation of the liner after compaction.

      Secondary  porosity  affects the hydraulic conductivity of the entire soil
 mass  and  generally  overrides the effect of primary porosity.  Thus, a son
 that  is composed of material of low matrix hydraulic conductivity can have a
 very  high  hydraulic conductivity because  of  secondary porosity.

      Many  natural clays  have joints.  Joints can result from postdeposi-
 tional expansion and  contraction from wetting and drying.  Joints and fis-
 sures in  preconsolidated clays result from shrinkage cracking and unloading.
 Cracks can also occur in clays that have  a water content consistently above
 the shrinkage limit.  These  cracks have been postulated to result from
 syneresis—the  formation of  closely knit  aggregates from the mutual attrac-
 tion  of clay particles or from the removal of potassium by weathering.
 Figure 2-10 shows a fracture in a glacial till with a low matrix permeabil-
 ity.  Root systems  can cause cracks by sucking up water, causing desiccation
 cracks to  develop in  the soil mass, and can  leave holes in the soil mass
 after rotting away.   Figure  2-11 shows a  root cast in a till, including a
 fracture  and a  zone of higher  hydraulic conductivity material left after
 roots have decayed.   Griffin et al. (1985) found in a study of a site in
 Illinois  that hydraulic  conductivities measured in the laboratory were much
 lower than conductivities measured by three methods in the field; they con-
 cluded that small laboratory specimens, whether 'undisturbed' or recompactecl,
 were  unable to  simulate  the  flow through  relatively large joints or partings
 present in natural  materials.

     The  ability of fissures or holes to  heal in a soil depends largely upon
 soil moisture content, soil  plasticity, the  size of the fissure or hole, and
 ambient stress.  Wetter, more  plastic soils  have a greater healing capability
 (USDI, 1974).   Certain organic chemicals  can affect a soil's self-healing
 capability by reducing a soil's moisture  content and .plasticity.

     Zones of permeable material in a soil with low hydraulic conductivity
 are generally referred to as lenses and seams and may be composed of silt and
 sand.  In  certain soil deposits, lenses are  isolated and discontinuous and
 have  little influence on the overall hydraulic conductivity of the soil mass
 and on potential contaminant migration.  However,  in other soils, these
 lenses may be continuous in one or more directions,  in which case they
 greatly increase a  soil's overall  hydraulic conductivity and provide poten-
 tial pathways for the rapid migration of contaminants in the groundwater.
Continuous zones of permeable material  are usually deposited by moving water
and are common in river floodplain deposits,  around  the perimeter of lake
deposits,  and in glacial  outwash deposits.  Permeable zones  also may be pres-
ent in marine and glacial till  deposits.   Figure 2-12 depicts a sand seam
outcropping in an otherwise low hydraulic conductivity (K^10~7 cm/s)  glacial
till.   Leachate from a nearby landfill  has migrated  through  this  sand seam and,
by evaporating,  has  left  white  salt crystals  that  outline  the sand  seam on the
surface of the cut.

                                    2-27

-------
   Source: Photo courtesy of Wisconsin Department of Natural Resources
Figure 2-10.  Fractures in glacial till. Note pen for scale (arrow).
                            2-28

-------
              Source: Photo courtesy of Wisconsin Department of Natural Resources
Figure 2-11. Root cast in glacial till. (Root cast is the lighter colored material in the
              right center. Note fracture that has developed along root cast (arrow).)
                                   2-29

-------
 Source: Photo courtesy of Wisconsin Department of Natural Resources
Figure 2-12.  Permeable strata in glacial till deposit. (Permeable zone is the outlined band
              across the center of photo. Note white salt crystals on surface of permeable
              zone left by evaporating leachate flowing from a nearby landfill.)
                                       2-30

-------
     For residual soils, products of chemical weathering of rocks in place,
the primary and secondary porosity-is influenced by the degree of weathering
and the composition and structure of the parent rock.  Fractures and fis-
sures in the parent rock may persist in the weathered mass (although not in
highly weathered deposits), affecting the secondary porosity.  Hydrothermally
deposited veins of quartz in the original rock can weather into veins of sand
in the resulting residual soil.  In addition, for soils derived from strati-
fied rock, the different rock strata can result in a soil with strata of
different hydraulic conductivities.

     Anisotropy and heterogeneity are common in all soils.  Anisotropy and
heterogeneity can be attributed to the existence and variation of primary
and secondary porosity.  On a small  scale, theoretical considerations have
led to the attribution of anisotropy to the orientation of clay minerals and
the effect the orientation has on primary porosity.  On a larger scale, a
relationship exists between heterogeneity and anisotropy (Freeze and Cherry,
1979).  Heterogeneities can be attributed largely to secondary porosity and
stratification in low-permeability soils.  Trending heterogeneities, where
transport parameters (e.g., hydraulic conductivity) change gradually in a
given direction, also exist in fine-grained, low-permeability soils.
Trending heterogeneities are most common in soils deposited in deltas,
alluvial fans, and glacial outwash plains (Freeze and Cherry, 1979).

     It should be stressed that secondary porosity, if present and inter-
connected, can completely override the primary porosity of a soil mass,
making a deposit of low-permeability matrix material highly permeable.  The
prevalence of heterogeneities in natural soil deposits is the primary reason
that hazardous waste containment facilities should be lined regardless of the
hydraulic conductivity of the in situ soil.

     Heterogeneities and anisotropies in soils can lead to significant dif-
ferences between field and laboratory permeability measurements (Olson and
Daniel, 1981; Griffin et al., 1985).  There are at least three factors
contributing to this difference:

     •     Most laboratory tests are set up to measure only vertical per-
           meability, while field permeability test results are usually a
           function of both vertical and horizontal permeabilities.   In
           anisotropic soils, horizontal permeability can be higher  than
           vertical permeability, resulting in higher field test results.

     •     Bias in sample selection  is a factor for those soils cohesive
           enough to withstand handling so that cracking or breaking is
           avoided.  This leads to a predominance of measurements of matrix
           permeability rather than  bulk permeability.

     •     Samples taken for laboratory permeability tests are smaller than
           the area covered by field tests.  Field permeability tests are
           more likely to include heterogeneities such as fissures and zones
           of high-permeability material that can significantly increase soil
           permeability.
                                    2-31

-------
      Because of these factors,  properly  performed  field permeability measure-
 ments can give a more accurate  estimate  of  soil permeability than can lab-
 oratory permeability tests  that are  run  on  "undisturbed" samples (Griffin
 et al., 1985;  Day and Daniel,  1985).   For soils with heterogeneities that
 affect permeability, the  larger the  field permeameters or the more that are
 used  for a site investigation,  the more  accurate will be the measure of the
 soil's permeability.  These factors  should  be considered when the protec-
 tlveness of potential  hazardous waste  facility sites is evaluated and during
 the measurement of hydraulic conductivity of compacted clay liners.

  2.4.2  Soil Structure and  Hydraulic Conductivity  in Compacted Soils

      Compaction is the application of  force to a soil to reduce the percent-
 age of air-filled voids and thus to  increase its density.  For cohesive
 soils,  of which clay liners are composed, compaction with a given type and
 amount of compactive effort at  various water contents will result in a,com-
 paction curve  such as  the one shown  in Figure 2-13.  Examination of this
 curve shows  that,  with a given  compactive effort, a maximum density is
 achieved at  a  certain  water content.  This  is the optimum water content for
 this  type and  amount of compactive effort.  The "S" lines in this figure
 represent the  computed relationship between water content and dry density at
 a  constant degree  of saturation.

      Figure  2-14  illustrates that the moisture/density relationship for a
 given  soil also depends upon the type and amount of compactive effort.  This
 figure  shows that  the  line  of optimum moisture contents and maximum dry den-
 sity  for these  compactive efforts approximately parallels the line of con-
 stant  saturation.   This figure  also shows that the type of compactive effort
 influences the  shape of the moisture content/density curve (see Chapter 3).
                                         i
     Much  earthwork  compaction  is directed toward achieving structural  sta-
 bility,  as with roadbed or  foundation compaction.  For these applications,
 strength,  stability, and resistance to changes in volume are the important
 parameters.  Density is used to  control these parameters in the field.
 Figures  2-13 and 2-14  illustrate that the same density can be achieved either
wet or  dry of optimum.  In many  cases, foundations and roadbeds are compacted
 dry of  optimum  for greater  shear strength because soil  shear strength de-
 creases with Increasing moisture content (Mitchell, 1976).  However,  when
 cohesive  soils  are compacted to achieve lower hydraulic conductivity, both
 the dry density (reduction of air voids)  and the fabric of the soil  are
 important.  Molding water content becomes important when attempts are made to
 rearrange the fabric of the clay.

     The  reduction of  hydraulic conductivity during the compacting  of a
cohesive soil 1s a function of the following two processes:

     •     The  reduction of the voids in  the soil

     •     The rearrangement of the fabric  of a  soil  to a  more  dispersed
           structure.
                                    2-32

-------
    18.5
(-'
5
^-
Z   18.0
  c
  Q
       17.5
                i
0.41


0.43



0.46



0.49



0.52
                                                         e
                                                         a
                                                         5
                «    8   10   12   14   16   18


                    WATER CONTENT w(%)
Source: Lambe, 19S5
 Figure 2-13. Compaction curve from a standard compaction test.
                          2-33

-------
                         19
                      g  18
                      2
                      JC
                         17
                      S  16
                      e
                      Q
15
                                           I
                                10        15  |      20

                                      WATER  CONTENT (%)
                                    25
No.
1
2
3
4
Layers
5
5
5
3
Blows per
Layers
55
26
12
25
Hammer
Mass
4.54 kg
5.54
4.54
2.50
Hammer
Drop
457 mm (mod. AASHO)
457-
457 (std. AASHO)
305
Source: Lambs and Whitman, 1979
    Figure 2-14. Compaction curves for different compactive efforts applied to a silty clay.
                                         2-34

-------
 In a dispersed soil structure, the clay mineral  platelets are oriented in a
 face-to-face fashion.  A dispersed structure has smaller pores than a more
 flocculated (edge-to-face) soil structure and also has more tortuous paths
 for liquid movement through the soil, resulting  in a lower hydraulic
 conductivity.

      Factors that influence the extent to which  compaction acts on  a cohesive
 soil  fabric to produce a more dispersed structure include:

      •     Molding water content

      t     Dispersivity of the clay minerals in  a soil

      •     Amount of compactive effort

      •     Type of compactive effort.

      Molding water content strongly influences the ease of rearranging clay
 particles and particle groups under the compactive effort used (Mitchell
 et al.,  1965;  Carpenter, 1982).  The profound effect of molding water content
 on soil  hydraulic conductivity is shown in Figure 2-15.  This  figure illus-
 trates that, for clay samples compacted to the same dry density at  different
 water contents, permeability decreases with increasing  moisture content,  and
 this  decrease can be more than 3 orders of magnitude (Mitchell,  1976).
 Permeability has also been shown to be strongly  affected by the amount and
 type  of  compactive effort used to reach the desired density (Mitchell  et  al.,
 1965).  Because of these phenomena, clay liner designs  should  specify that
 clay  liners be compacted wet of optimum and moisture content,  density,  and
 compactive effort measured and controlled for proper clay liner compaction.
 If only  density is specified or measured and moisture content  and compactive
 effort are not carefully controlled,  the specified density can  be achieved at
 too low  a moisture content,  resulting in a liner  with a higher  hydraulic
 conductivity than required.

      Soil  dispersivity is  affected  by the double-layer  thickness of  the clay
 minerals  in  the soil.   Soils  composed of minerals  with  thicker  double  layers
 have  higher  dispersivities.   The  dispersivity of  clay minerals  in a  soil
 affects  its  hydraulic  conductivity.   Figure  2-16  illustrates this phenomenon,
 showing  that adding  a  chemical  dispersant  to a soil  reduces hydraulic  conduc-
 tivity upon  compaction.   (The  chemical dispersant  increases the double-layer
 thickness  of the  clay minerals.)

     A liner soil must  be  carefully screened as it arrives onsite to ensure
 that the arriving  soil  type remains the same.  If a change in soil  type
 occurs, it could  have a  lower dispersivity.  If this soil is compacted
according  to soil  compaction parameters  (density  and moisture content)
developed  for the original soil, a more permeable liner could result.  Thus,
 if the soil characteristics change during the construction of a clay liner
 it is  necessary to reestablish density/moisture content/compactive
effort/hydraulic conductivity relationships for the new soil before  it is
used as a liner material.
                                    2-35

-------
  o
  
 £
     1x10
          -9
                     Saturation = 95%
                 12
>

l€
S  i
>  ^
a:
a
         114
         106
                         14
                     Kneading
 t     i

16
13
                 compaction curve  *••...
                                        r
                                  Density of Samples
                                          I
 i

20
                          Line of optimums
                      13        15       17        19

                     MOLDING WATER  CONTENT (%)
Source: Mitchell, 1976
Figure 2-15.  Permeability as a function of molding water content for samples
    of silty clay prepared to constant density by kneading compaction.
                             2-36

-------
   1x10'~S  I-
o
e
u
I  1*10'
o
>  1x10~7
<
CO
                10   11   12   13   1*   15

                MOLDING WATER CONTENT
                     (% dry soil mass)
                                                       20.0
*  19.0

Z

>  18.0
0
                                                                0=0.1
            10   11   12   13   14   15

          MOLDING. WATER CONTENT
               (% dry  soil  mass)
    Source:  Lambe, 1955.

        Figure 2-16. The effect of dispersion on hydraulic conductivity. D = 0 is compaction
                    curve for a soil compacted in its natural state; D = 0.1 is a compaction
                    curve for a soil compacted with 0.1% (of dry soil weight) of sodium-
                    polyphosphate.
                                         2-37

-------
     The method of compaction also affects the hydraulic conductivity of a
compacted soil liner.  Figure 2-17 illustrates that, for a cohesive soil com-
pacted to the" same density, kneading compaction results in a lower hydraulic
conductivity than static compaction.  This occurs because kneading action
introduces shear strains to the soil, which tends to realign particles and
results in a more dispersed soil fabric (Mitchell, 1976).  This phenomenon
occurs only for cohesive soils compacted wet of optimum because the clay
particles can be rearranged easily only at a high moisture content.  This
phenomenon is the reason for a general preference for sheepsfoot rollers for
compacting clay liners; although equivalent densities at a given moisture
content may be obtained with a smooth-wheeled roller, the kneading action of
the sheepsfoot should result in lower hydraulic conductivities for most
soils.

     The effect of method of compaction on soil fabric is partly responsible
for the difference observed between field and laboratory compaction methods
(Lambe and Whitman, 1979).  Laboratory compaction methods generally result in
permeabilities lower than those attained using field equipment (Dunn and
Mitchell, 1984; Day and Daniel, 1985).  This is because compactive efforts
used in laboratory compaction tests are not the same as those produced by
specific field compaction equipment.  Thus it is necessary to compact a
test fill in the field and conduct permeability tests on this material to
verify laboratory results (see Section 5.3.3.1.1).

2.5 REFERENCES

Acar, Y.B. and R. K. Seals.  1984.  Clay Barrier Technology for Shallow Land
    Waste Disposal  Facilities.  Hazardous Waste.  1(2):167-181.

ASTM.  1985.  American Society of Testing Materials Annual Book of ASTM
    Standards.  Vol. 04.08.

Carpenter, G. W.  1982.  Assessment of the Triaxial Falling Head Perme-
    ability Testing Technique.  Ph.D. dissertation, University of Missouri,
    Rolla, Missouri.

Chapman, D. L.  1913.  A Contribution to the Theory of Electrocapillarity.
    Philosophica Magazine.  25(6):475-481.
                                                     «
Daniel, D. E.  1984.  Predicting Hydraulic Conductivity of Clay Liners.
    Journal of Geotechnical Engineering.  110(2):285-300.

Day, S. R. and D. E. Daniel.  1985.  Hydraulic Conductivity of Two Prototype
    Clay Liners.  ASCE Journal of Geotechnical Engineering.  August 1985.
    111(8):957-970.

Deer, W. A., R. A. Howie, and J. Zussman.  1966.  An Introduction to the
    Rock-Forming Minerals.  Longman Group Limited.  London.

Dunn, R. J. and J. K. Mitchell, 1984.  Fluid Conductivity Testing of Fine
    Grained Soils.  J. of Geotechnical Engineering.  110(11):1648-1665.

Fisher, W. L.  1965.  Rock mineral resources of east Texas:  Texas University
    Bureau of Economic Geology.  Report of Investigations 54.  439 pp.
                                    2-38

-------
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              CD
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              er
                    3.
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                                  x
                                  3
                                 a
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o

3   «   o

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r-   »   e

§   a   s

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-*   3   3


M



in
                         §
                                                      DRY DENSITY


                                                        (Ib/ll3)
                                                             HYDRAULIC  CONDUCTIVITY (cm/aoc)
   O   3



   3   -
   O   u.
             o

             5
                                      m
                                      3)

                                      o
                                      o
                                      z

                                      ni
                                      z
o


O

Z
O
                                                  -I
                                                  m
                                                  3J

                                                  O
                                                  O
                                                  z

                                                  m
                                                  z
                                                  H

-------
Freeze, R. A., and J. A. Cherry.   1979.   Groundwater.  Prentice-Hall, Inc.
    Englewood-Cliffs, New Jersey.

Gouy, G.  1910.  Sur la Constitution de  la Charge  Electrique a la Surface
    d'un Electrolyte.  Anniue Physique (Serie  4) 9:457-468.  Paris.

Griffin, R. A., B. L. Herzog, T.  M.  Johnson, W. J.  Morse, R. E. Hughes,
    S. F. J. Chou, and L. R. Follmer.  1985.   Mechanisms of Contaminant
    Migration Through a Clay Barrier-Case Study, Wilsonville, Illinois.
    Eleventh Annual Research Symposium,  U.S. Environmental Protection Agency,
    Cincinnati, Ohio.  EPA/600/9-85/013. , p. 27-38.

Grim, R. E.  1962.  Applied Clay  Mineralogy.   McGraw-Hill.  New York.

Grim, R. E.  1968.  Clay Mineralogy  (second edition).  McGraw-Hill.
    New York.

Heath, R. C.  1984.  Groundwater  Regions of the United States.  Water
    Supply Paper 2242.  United States Geological Survey, Reston, Virginia.

Hilf, J. W.  1975.  Compacted Fill.   Chapter 7 in  Foundation Engineering
    Handbook.  Eds., Winterkorn,  H.  F.,  and H-Y. Fang.   Van Nostrand Reinhold
    Co.  New York.

Hosterman, J. W.  1984.  Ball Clay and Bentonite Deposits of the Central and
    Western Gulf of Mexico Coastal Plain, United States.  U.S. Geological
    Survey Bulletin 1558-C.  USGS; Alexandria, Virginia.

Hosterman, J. W.  1985.  Bentonite and fuller's earth resources of  the  United
    States.  Mineral Investigation Resources  Map:   MR-0092.  U.S Geological
    Survey; Alexandria, Virginia.

Holtz, R. D., and W. D. Kovacs.  1981.  An Introduction  to  Geotechnical
    Engineering.  Prentice Hall,  Inc.  Englewood Cliffs, New Jersey.

Johnson, A. T., and D. A. Morris.  1962.  Physical and Hydrological
    Properties of Water-Bearing Deposits From Core Holes in the  Las Barros—
    Kettleman City Area, California.  USGS, Open File, Department,  Denver,
    Colorado.

Keller, W. D.  1964.   Processes of Origin and Alteration of Clay Mineral.
    Eds., Rich, C. I., and G. W. Kunze Soil Clay Mineralogy.   University of
    North Carolina Press, Chapel  Hill.

Kozicki, P.,  and  D. M. Heenan.  1983.  Use of Bentonite as  a  Soil  Sealant  for
    Construction  of Underseal Sewage  Lagoon Extension, Glenboro,  Manitoba.
    Shortcourse on Waste Stabilization Ponds,  Winnipeg,  Manitoba.

Lambe, T. W.  and  R. T. Martin.  1953-1957.  Composition and Engineering
    Properties of Soil.  Highway Research Board Proceedings.   1-1953,
    11-1954,  III-1955,  IV-1956, V-1957.

Lambe, T. W., and R. V. Whitman.  1979.  Soil  Mechanics (SI version).   John
    Wiley and Sons,  Inc. New York. ,     .
                                     2-40

-------
 Mason,  B.,  and L.  G.  Berry.   1968.   Elements of Mineralogy.  W. H. Freeman
      and Co.   San  Francisco.

 Mitchell, J.  K.  1976.   Fundamentals  of Soil Behavior.  John Wiley and Sons,
     Inc. New York.

 Mitchell, J.  K., D. R.  Hooper, and R. G. Campanella.  1965.  Permeability of
     Compacted Clay.   Journal  of  the Soil Mechanics and Foundations Divisions,
     A.S.C.E.   91(SM4):41-65.

 Olson,  R. E.,  and  D.  E.  Daniel.   1981.  Measurement of the Hydraulic
     Conductivity of Fine-Grained  Soils.  ASTM STP 746,:18-64.  ASTM.
     Philadelphia,  Pennsylvania.

 Parks,  G. A.   1975.   Adsorption  in the Marine Environment.  Eds., Riley,
     J.  P.,  and  G.  Skirrow.  Chemical Oceanography 1.  (second edition)
     241-308.  Academic Press.  New.York.

 Patterson,  S. H. and  H.  H. Murray.  1984.  Kaolin, Refractory Clay, Ball
     Clay, and Hallosite  in North America, Hawaii,  and the Caribbean Region.
     Prof. Paper 1300.  U.S. Geological Survey.  Alexandria, Virginia.

 Perloff,  W. H., and W. Baron.  1976.  Soil  Mechanics.  Ronald Press Co.
     New  York.

 Rogowski, A. S., and  E.  B. Richie.  1984.  Relationship of Laboratory and
     Field Determined  Hydraulic in Compacted Clay Soils.  Proceedings of the
     16th  Mid-Atlantic Industrial  Waste Conference.  The Pennyslvania State
     University, University Park,  Pennsylvania.

 Sangrey,  D. A., D. K. Noonan, and G. S. Webb.  1976.  Variation in Atterberg
     Limits  of Soil Due to Hydration History and Specimen Preparation.  Soil
     Specimen Preparation for Laboratory Testing, ASTM STP 599,  American
     Society for Testing  and Materials,  pp. 158-168.

 Stern, 0.   1924.   Zur Theorie der Elektrolytischen Doppelschrift.
     Zietschrift Electrochem.  30:508-516.

 Stumm, W., and J.  J. Morgan.  1970.  Aquatic Chemistry.  John Wiley and Sons,
     Inc.  New York.

 Theng, B. K. G.  1974.  The Chemistry of Clay-Organic Reactions.   John Wiley
     and Sons, Inc.  New York.

 U.S. Dept. of Interior (USDI).  1974.  Earth Manual  (second edition).  U.S.
     Government Printing Office, Washington, D.C.

 Van Olphen,  H.  1963.   An Introduction to Clay Colloid Chemistry.   Wiley
     Interscience.  New York.

Weaver,  C. E., and L.  D. Pollard.  1973.  The Chemistry of Clay Minerals.
    Developments in Sedimentology 15.   Elesevier,  Amsterdam.
                                    2-41

-------
Wlnterkorn, H. F., and H-Y. Fang.   1975.   Son  Technology and Engineering
    Properties of Soils.  Chapter  1 In: Foundation  Engineering Handbook.
    Eds., Wlnterkorn, H. F., and H-Y.  Fang.   Van  Nostrand Reinhold.
    New York.
                                   2-42

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                                 CHAPTER 3

                     TEST METHODS AND SOIL PROPERTIES
3.1  INTRODUCTION
     The engineering properties of soils are as varied as their chemical
compositions, their modes of formation, and their past and present environ-
mental settings.  Consequently, when designing and constructing earthwork
projects, the design or construction engineer is faced with determining
whether or not a particular soil is suitable for its intended application.
To aid this decisionmaking process, a wide assortment of test procedures
have been developed that are used either to predict the probable engineering
performance of a soil (index tests) or to measure the soil performance
directly with respect to parameters of concern (e.g., permeability and shear
strength).

     This chapter presents and discusses the soil testing procedures that
are of particular interest to designers of clay liners for hazardous waste
containment facilities.  Emphasis is on determining Atterberg limits and
density, compaction, and permeability testing, with the bulk of the chapter
devoted to the latter.

     Many test procedures have been standardized by organizations like
the American Society of Testing and Materials (ASTM) and are applied
routinely and uniformly by all competent soil testing groups (ASTM, 1984).
Permeability testing, on the other hand, has not.been standardized.
Different types of permeability testing equipment are in current use, and
test protocols also can vary from laboratory to laboratory and even from
test to test within a laboratory.  The situation is further complicated by
the need to measure not only the permeability to water but also, and perhaps
more importantly, the permeability to leachates or other complex chemical
mixtures.  In addition, there is much discussion and controversy among soil
experts concerning the interpretation of permeability test results, the
relationship between field and laboratory permeability testing, and the
relative merits of different types of testing equipment and test protocols.

     Many soil tests, because of their routine nature and the general
availability of the test protocols, are not discussed in detail in this
chapter.  However, capsule summaries of many important tests are provided
in Appendix A.  These summaries have been taken directly from the EPA docu-
ment Geotechnical Quality Assurance of Construction of Disposal Facilities
(Spigolon and Kelly, 1984).The summaries are intended only to give the
reader general information about the specific test methods.  More detailed
information can be obtained from the references noted for each test.  A list
                                     3-1

-------
 of the  summarized  tests  contained  in Appendix A  is provided in Table 3-1.
 Other important  soil  test  procedures may be found in the ASTM Standards,
 Part  19 -  Natural  Building Stones; Soil and Rock (ASTM, 1984).

      One of the  most  commonly  used pieces of field test equipment is the
 nuclear moisture and. density gauge.  This device provides a rapid and reli-
 able  means  of making  in-place  field measurements of the moisture content
 and density of soil.   However,  for accurate measurements in all test circum-
 stances, it is necessary to understand the theoretical basis of the tests and
 to be mindful of certain caveats Regarding the application of nuclear soil
 testing techniques.   For these  reasons, nuclear methods are described in
 detail  in Section  3.6.2.

 3.2   FUNDAMENTAL RELATIONSHIPS

      The presence  of  liquid and gas-filled voids in soils is an inescapable
 consequence  of the particulate nature of the material.  The multiphase nature
 of soils is  diagramatically represented in Figure 3-1, which depicts the
 fundamental  relationships  of the weights and volumes of the basic components
 of a  soil mass.  For  soil  engineering purposes, the important parameters are
 unit weight, void  ratio, porosity, and degree of saturation.  The measure-
ments that are made to compute these parameters are the weight and volume of
 the wet specimen, the weight of the same specimen after drying, and the
 volume  of the solids.  Discussion of the appropriate standard procedures for
 these measurements can be  found in Laboratory Soil  Testing, U.S. Department
 of the Army  (1970); in ASTM (1984); and in Appendix A of this document.

3.2.1  Water Content

     A fundamental  property of any soil is its water content.  This is de-
fined as the ratio, expressed as a percentage, of the weight of water in a
given soil  mass  to the weight of the solid particles.

3.2.2  Density

     The density of a material  is its mass per unit volume.  As a consequence
of voids being an integral  part of any soil, soil may be considered to have
two "densities."  One of these densities,  called the dry or solid density, is
that of the  solid particles.  The other density, calfed the total  or wet
density, is  the density of the total  soil  mass including water- and
air-filled voids.

3.2.3  Specific Gravity

     Specific gravity (of solids), Gs,  is  defined as the ratio of the density
of solid particles, Ps, at a stated temperature to  the density of dis-
tilled water, Pw, at 4° C:


                               Ps           W.

                          Gs-p-0rGs=HT                        (3<1)
                                w          s   7w
                                     3-2

-------
                 TABLE 3-1.   SOIL  TESTS  SUMMARIZED  IN APPENDIX A
                                                                  Method
                           Method                                  number3
  Parameter measured:  water  content
      Standard oven-dry                                              j
      Standard nuclear moisture/density gauge                        2
      Gas burner      i                                               3
      Alcohol burning                       -                         4
      Calcium carbide (speedy)                                       5
      Microwave oven                                                 g
      Infrared oven                                                  7
  Parameter measured:  unit weight
      Standard laboratory volumetric                                 8
      Standard laboratory displacement                               g
      Standard field sand-cone                                       in
      Standard field rubber balloon                                  11
      Standard field drive-cylinder                                  12
      Standard nuclear moisture/density gauge                        13
 Parameter measured:  ispecific gravity
      Standard laboratory                                            14
 Parameter measured:  grain-size distribution
      Standard sieve analysis (+200 fraction)                         15
      Amount  of soil finer than No. 200 screen  (wash)  standard        16
      Standard laboratory hydrometer (-200 fraction)                  17
      Pipette method for  silt and clay fraction                       18
      Decantation  method  for  silt and  clay fraction                   19
 Parameter measured:  liquid  limit
      Standard multipoint                                            20
      Standard one poiht                                              21
 Parameter measured:  plastic limit
      Standard laboratory                                            22
 Parameter measured:   cohesive  soil  consistency
      Standard unconfined compression                                 23
      Field expedient  unconfined  compression                          24
      Hand penetrometer                               *               25
      Hand-held torvane                                               26
 Parameter measured:  water content/density/compactive effort
      25 blow  standard;Proctor  compaction                             27
      25 blow modified;Proctor  compaction                             28
      Nonstandardized Proctor compaction                             29
      Rapid, one-point Proctor  compaction                            30
      Rapid, two-point Proctor  compaction                            TI
      Hilf's rapid                                                   32
      Ohio Highway Department nest of curves                         33
      Harvard miniature compaction                                   ™
                      i                                              JH
^	

aMethod numbers have been assigned for the sole purpose of providinq
 an easy way of finding the test method in the  appendix.  The number
 is meaningless outside of the context of this  document.
                                     3-3

-------
     Weight
     W w
         w
        We
                Air
              Water
Volume
                            i,   i
                        'w
                            9

                           Jj
             MOIST SOIL
Weight
                                                                  Volume
                                                  W,
                       W
                                                   w
                                                  W.
                                                         Water
                                          VWVV
                                                                         V
                                                     SATURATED SOIL
Figure 3-1.  Schematic representation of soil illustrating the fundamental relationships
            among the solid, liquid, and air constituents.
                                     3-4

-------
where
     7  = the-unit weight of water  (1.00 g/cm3 or 62.43 lb/ft3) at 4°C
      w

3.2.4  Unit Weight

     Dry unit weight 73  is defined  as the weight of the oven-dried
soil solids per total volume of the wet soil mass:


                                Ws
                           7d = -f                               (3.2)

     Wet unit weight ym  is the total weight (solids and water) per unit
volume of soil:


                                 rm = v                          (3-3)

Both wet and dry unit weights are usually expressed in pounds per cubic
foot (lb/ft3).

3.2.5  Void Ratio

     Void ratio, e, is the ratio of the volume of the voids to the volume of
the solids in a given soil mass:


                                  Vy    V - V

                              e = -v  = —r~                    (3-4)
                                    s      s
where


                              ws
     V_ = volume of solids = 7*-=—
      s                      Gs ^w

3.2.6  Porosity

     Total  porosity, n,  is the ratio, usually expressed as a percentage,  of
the total  volume of the  voids of a given soil  mass to the  total  volume of the
soil mass:


                            V           V - V
                        n =     x 100 =      s  x 100            (3.5)
                                     3-5

-------
      Effective porosity is  defined as  that fraction  of the  total  volume
 through  whlch-flow can occur.   If all  of the pores and void space contrib-
 uted  to  flow,  the effective porosity would simply equal  the volume of voids
 divided  by the total  volume.  However,  some pores in soil are  isolated or
 dead-end pores that do not  contribute  to flow.   Water that  is  tightly
 adsorbed to the wall.of a fluid-conducting pore  also decreases the flow area
 and effective  porosity.  The total  porosity typically ranges from 0.2 to 0.5
 for clays;  however,  the effective porosity in clay is thought  to  be on the
 order of 0.01  to 0.1  (Zimmie et al., 1981; Daniel, 1981; Horton et al.,  1987;
 Peyton et al.,  1986).

 3.2.7 Degree  of Saturation

      Degree of saturation,  S,  is the ratio (expressed as a  percentage)  of the
 volume of the  water in a soil  mass  to  the  total  volume of the  voids.
                                  S =
                                       w
(3.6)
3.3  ATTERBERG LIMITS
     Depending upon the water content, the consistency of a cohesive soil
may range from that of a viscous liquid to that of a very hard solid.  This
range of consistencies may be arbitrarily divided into the four stages illu-
strated in Figure 3-2, with the divisions between these states referred to as
the limits.  These limits are called the Atterberg limits after the Swedish
soil scientist, A. Atterberg, who in 1911 developed a series of tests for
determining the plasticity of cohesive soils.

     To understand the significance of the Atterberg limits, assume that a
very wet fine-grained soil is slowly dried.  In the very wet condition, the
soil will act like a viscous liquid.  As it dries, a reduction in volume
occurs that is very nearly proportional to the water loss.  When the water
content is reduced to the value of the liquid limit, the soil consistency
becomes plastic (i.e., the soil mass can be shaped or deformed without
cracking).  The liquid limit is determined experimentally using the device
illustrated in Figure 3-3.  The soil sample is placed,in the cup of the
apparatus and a specially designed tool is used to cut through the sample
(Figure 3-4).  To perform the test, the crank is turned causing the sample
cup to be tipped up by a cam and then dropped onto the hard surface below it,

                                   Stages of consistency
                                       _A
rSolid
stata

Semisolid
stata

Plastic state
Range indicated by
the plasticity index (PI)
PI - LL-PL
Liquid state

SL PL LL
                  Sourca: U.S. D«pt of Interior, 1974
             Figure 3-2.  Consistency limits of cohesive soils.

                                     3-6

-------
Figure 3-3.  Device for determining the liquid limits of a cohesive soil. The dish contains a
            grooved sample.
             Figure 3-4. Clay sample being grooved for liquid limit test.
                                     3-7

-------
thereby supplying a "blow" to the soil  sample.   The liquid  limit  is  defined
as the water content at which one-half inch of  the groove is  closed  after 25
blows (U.S. Department of Interior, 1974).

     In practice, while it is hard to adjust the soil  moisture  so that  the
groove closes at exactly 25 blows, the liquid limit can  be  determined by
plotting the water contents at which closure occurs with other  blow  counts
against the log of the number of blows needed to achieve groove closure.
This procedure produces a straight line known as the flow line  from  which
the water content corresponding to groove closure at 25  blows can be found
easily.  This method is described in ASTM method D4318 (ASTM, 1984).

     A one-point liquid limit test also can be  performed provided that  the
practitioner is already familiar with the soils from which  the  sample is
obtained.  The basis for the one-point procedure is the  fact  that the slopes
of the flow lines for soils within a given soil environment are generally
constant.  Therefore, if the flow line slope, the water  content,  and the
number of blows to obtain closure at that water content  are known, the  liquid
limit can be computed from the following formula:
                           LL = WN
                                           ('tan 0 \                     (3.7)

where

        WN » water  content of sample

         N = number of blows required to !close the groove

     tan 0 = slope  of the flow line.

The one-point test  is usually performed on soil samples prepared to a con-
sistency that requires 20 to 30 blows to close the groove (U.S. Department
of the Army, 1970).  A one-point liquid limit test method is described in
ASTM method D4318 (ASTM, 1984).

     As the water content 1s reduced below the liquid limit, the soil mass
becomes stiffer and will no longer flow.  The soil  w1Jl continue to be
plastic (deformable) until the plastic limit is reached.  The plastic limit
is defined as the water content, expressed as a percentage of the weight of
the oven-dried soil, where the soil begins to crumble when rolled Into a
thread 1/8 inch in diameter (U.S. Department of the Army, 1970).,  The rolling
and crumbling are Illustrated 1n Figures 3-5 and 3-6.  The test method for
determining the plastic limit 1s ASTM D 4318 (ASTM, 1984)

     As stated earlier, a soil  mass will decrease 1n volume 1n proportion to
the amount of water removed.  However, 1f enough water is removed, a point
will be reached below which very little shrinkage will occur.  The moisture
content at this point, which is referred to as the shrinkage limit, divides
the solid from the semlsolid phases in the soil consistency continuum
(Figure 3-2).  Below the shrinkage limit, the soil  is considered a solid.
In most fine-grained plastic soils, the plastic limit will be appreciably
greater than the shrinkage limit.  However, for coarser grained soils, with
predominantly coarse silt and fine sand sizes, the shrinkage limit will  be
                                    3-8

-------
            Figure 3-5.  Rolling a clay sample for plastic limit test.
      *  *

                                          "*

Figure 3-6. Results of rolling clay with moisture content below the plastic limit.
                                    3-9

-------
 near the plastic limit (U.S. Department of Interior,  1974).   The  test
 procedure for determining the shrinkage limit is ASTM D  427  (ASTM,  1984).

      Very often the term plasticity index is encountered.  It is  the
 numerical difference between the liquid limit and the plastic limit and
 represents the range of moisture within which the soil  remains plastic.

      The plasticity index can be used to compute the  activity, A, of a
 cohesive soil.  A is the ratio of the plasticity index to  the percentage of
 clay-size particles (smaller than 0.002 mm)  and  is an expression  of the
 plasticity of the clay fraction of the soil.  The mineralogy  of the clay
 fraction is suggested by the activity, with  low  activity (less than 1)
 characteristic of kaolinite, high activity (greater than 4) characteristic of
 montmorillonite, and intermediate activity (1-2)  characteristic of  illite
 (Sowers and Sowers, 1970).

      Soils may be grouped and located on a plasticity chart according to
 their liquid limits and their plasticity indices  (Figure 3-7). The location
 of a soil on the chart provides a basis for  estimating  its engineering
 properties based on knowledge of other tested soils that plot in  the same
 region of the chart.  The plasticity chart is roughly divided into quadrants
 by the "A" line and the 50-percent liquid limit  line. Soils  that plot above
 the "A" line are classified  clays; those below are not clays.   The 50-percent
 liquid limit line is an arbitrary division between high  and low liquid limit
 soils.  In general, soils plotting above the "A"  line have low
 permeabilities; for soils with the same liquid limit,  the greater the
 plasticity index the greater the strength at the  plastic limit;
 compressibility increases with increasing liquid  limit  (U.S.  Department of
 Interior, 1974).

 3.4  SOIL CLASSIFICATION

      Based upon his early field work,  Professor A.  Casagrande  of Harvard
 University developed a soil  classification system  for grouping  soils by a
 plot  of their plasticity  index versus  their  liquid  limit.  In  1942,  the U.S.
 Army  Corps of Engineers adopted this  system  for airfield work.  The system
 was modified  slightly in  1947  to prevent  dual  classification of soils;  in
 1952  the  U.S.  Bureau of Reclamation and  the  U.S. Army. Corps of Engineers, in
 consultation with Dr.  Casagrande,  adopted  the  system under the title of the
 Unified Soil  Classification  System (USCS).   The USCS  is descriptive, easy to
 use,  adaptable  to field or laboratory  use, and takes  into account  the  soils'
 engineering properties.   One of  its greatest advantages is that a  soil  can  be
 classified  readily  by  visual and manual examination without extensive
 laboratory  testing.  The  system  is based on  the size distribution  of the soil
 particles and the activity of  the  very fine grains  (U.S. Department  of  the
Army, 1953; U.S. Department of  Interior, 1974).

3.4.1  Grain Size Analysis

     Within the USCS,  soils are divided into  coarse-grained and fine-grained
types.  Coarse grains are larger than the openings in  the U.S. Standard
Series No. 200 sieve; fine grains can pass through the No.  200 sieve.  The
                                     3-10

-------
  ISO
  160
  140
  120
x
Ul
a
z
  100
  80
  60
  40
   20
 SANOY CLAY, NORTHEASTERN NEW MEXICO.
 SILTY LOESS, KANSAS-NEBRASKA
 CLAYEY LOESS,KANSAS.
 KAOLIN CLAY, DECOMPOSED GRANITE,SINGAPORE.'
 KAOLIN CLAY, RESIDUAL SOIL,CALIFORNIA.
 SILTY CLAY, SALT LAKE BASIN SEDI MENTS,UTAH.
 PORTERVILLE CLAY "EXPANSIVE" (CALCIUM
  BEIOELLITE ) , CALIFORNIA.
 HALLOYSITE CLAY, SANOY , TRACE OF
  MONTMORILLON.ITE, GUAM .MARIANAS ISLANDS.
 TULE LAKE SEDIMENTS (DIATOMACEOUS AND
  PUMICE), NORTHERN CALIFORNIA.
 MONTMORILLONITE CLAY, S-LI.GHTLY ORGANIC,
  GUAM, MARIANAS ISLANDS.
> CLAY.GLACIAL LAKE DEPOSIT, NORTH DAKOTA.
 CLAY,"EXPANSIVE" (SODIUM MONTMORILLONITE)
  GILA RIVER VALLEY, ARIZONA.
i BENTONITE,WYOMING  AND SOUTH
  DAKOTA.
                                                200       400      600
                                                   LIQUID LIMIT
                                  80      100      120
                                    LIQUID LIMIT
                                              140
160
180
200
     Source: U.S. Department of Interior, 1974
                  Figure 3-7.  Typical relationships between the liquid limit
                         and the plasticity index for various soils.
                                      3-11

-------
particle  size distribution of coarse-grained soils can be determined readily
by a  sieve analysis, wherein the sample is passed through a set of sieves and
the material retained on each sieve  is weighed (U.S. Department of the Army,
1970).  Sieve sizes commonly used are listed in Table 3-2.

      The  size distribution of particles smaller than the No. 200 sieve can
be determined by the hydrometer or by the pipette method based on Stokes1
Law,  which relates the terminal velocity of a sphere flowing freely through
a fluid to the sphere's diameter.  The relationship is expressed as;


                              v -  7s = 7F  D2                           (3.8)
                              V *  1,800 rj  U
where                                  :

      V  ~ terminal velocity of sphere, cm/s

      7  s density of sphere, g/cm3

      7  = density of fluid, g/cm3

      TJ  » viscosity of fluid, g-s/cm3

      D  » diameter of sphere, mm.

The test assumes that Stokes1 Law can be applied to a mass of dispersed soil
particles of various shapes and sizes.  The test is conducted by treating
the soil sample with a chemical dispersant and then mechanically dispersing
the sample in water to form a suspension.   Hydrometer readings or pipette
samples at a specific depth in the column are taken every several minutes,
and Stokes1 Law is used to compute the maximum grain size in suspension.

     Methods for determining grain size distribution are summarized in
Appendix A, Methods 15-19.  Directions for conducting the tests can be
found in U.S. Department of the Army (1970) and in ASTM Method D422-63
(ASTM, 1984).

     Grain size distributions are usually displayed graphically as illus-
trated in Figure 3-8, which plots graded and poorly graded distributions.
Well-graded soils have good representation of all  particle sizes over a
fairly broad size range.  A poorly graded  soil  may have an excess or
deficiency of particles within a certain size range (gap-graded or skip-
graded), or all  the particles occur within a fairly narrow range.

     The following coefficients have been  defined to determine whether a soil
is well  graded or poorly graded:


                                          Dfin                           (3.9)
          Coefficient of uniformity,  C  =  ^
                                      u   D
                                    3-12

-------
TABLE 3-2.  U.S. STANDARD SIEVE SIZES AND THEIR
         CORRESPONDING OPEN DIMENSION
U.S. standard                      Sieve opening
sieve number                           (mm)
      4                               4.75

     10                               2.00

     20                               0.85

     40                               0.425

     60                               0.25

    100                               0.15

    140                               0.106

    200                               0.075
                    3-13

-------
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-------
          Coefficient of curvature, C
                                     _
                                     c   U10 x U60

where  "D" with a numerical subscript represents the size that is larger
than a given percentage of the soil mass (as Indicated by the subscript).
As an  example, DIQ = 0.5 mm means that 10 percent of the sample by weight
is smaller than 0.5 mm in diameter.  To be well graded, the coefficient
of curvature (Cc) must be between 1 and 3 and, in addition, the coefficient
of uniformity (Cu) must be greater than 4 for gravels and greater than
6 for  sands.

3.4.2  The Unified Soil Classification System (USCS)

     Except for small editorial changes, the following sections (Sections
3.4.2  through 3.4.2.3.3) are taken. directly from the Earth Manual (U.S.
Department of Interior, 1974).

     Soils in nature seldom exist separately as gravel, sand, silt, clay, or
organic matter, but are usually found as mixtures with varying proportions of
these components.  The Unified Soil Classification System (USCS) is based on
recognition of the type and predominance of the constituents, considering
grain size, gradation, plasticity, and compressibility.  It divides soils
into three major divisions:  coarse-grained soils, fine-grained soils, and
highly organic (peaty) soils.  In the field, identification is accomplished
by visual examination for the coarse grains and by a few simple hand tests
for the fine-grained soils or fraction, as described in the classification
chart  (Figure 3-9 and fully described in Section 3.4.2.3).  In the labora-
tory, the grain-size curve and the Atterberg limits can be used in addition
to visual examination.  The peaty soils (Pt) are readily identified by color,
odor, spongy feel, and fibrous texture and are not further subdivided in the
classification system.

3.4.2.1  Field Classification—
     A representative sample of son  (excluding particles larger than 3
inches) is first classified as coarse grained or fine, grained by estimating
whether 50 percent, by weight, of the particles can be seen individually by
the naked eye.  Soils containing more than 50 percent. of Individual  particles
that can be seen are coarse-grained soils;  soils containing more than 50
percent of particles smaller than the eye can individually distinguish are
fine-grained soils.  (The No. 200 sieve size [74 /nn] particles are about the
smallest that can be seen individually by the unaided eye.)  If the soil is
predominantly coarse grained, it is then identified as being a gravel or
a sand by estimating whether 50 percent or more, by weight, of the coarse
grains are larger or smaller than the No. 4 sieve size (about 1/4 inch).

     If the soil  is a gravel, it is next identified as being "clean" (con-
taining few or no fines)  or "dirty" (containing an appreciable amount of
fines).  For clean gravels, final  classification is made by estimating the
gradation:   the well -graded gravels belong  to the GW group, and uniform and
                                    3-15

-------
 I
I-*
0>
UNIFIED SOIL CLASSIFICATION
INCLUDING IDENTIFICATIOH AND DESCRIPTION
FIELD IDENTIFICATION PROCEDURES
(deluding parliclis lorgtrjheA J uKMS V4 Dating frtctrtnt ottttunatid vtighlsl
Uort than holt of mettnoU jmoJ]jE than Na 200 sitvt tut. J Mart then tali of mattrwl is larftr than No, zoo swvt sut u
(Tht No. 200 titvt sttt is about tht snalltst oertKte visihtt to tht noktd tyt)
•KAVCLS
Uort than halt of coarst traction
sizt may bt ustd as tquivalmt
SAMDI
Mort than halt of coarst fraction
is smaller than No.4 sitvt silt
(For visual classifications, tht i"
totht NO.4 sitvt Slit,)
CLEAN (RAVELS
(Lift It er no
tinit)
MAVELS WITH
FINES
(Apprtcioblt
cmount of tints)
CLEAN SANDS
(Litllt or no
tints)
SANDS WITH
PINES
(Apprtcioblt
amount of tints)
IDENTIFICATION PROCEO
S SILTS AND CLAYS
Liquid limit
) Itss than 50
SI!
JH
HIGHLY CRSAH1C SOILS
Widl rongt in grotn tut ond iwbitontMj amounts
otMuitirmtdrttt parhcU lilts
fVidommanlly ont Hit or a rangt of Sim
with somt intirmidialt um mining.
Non-plastic finis (for idtntification proctdurts
sn UL btiow)
Plastic finis ((or idinhti cation prociduns
sit CL bllow)
Widt rangt in gram tills ond substantial
amounts of all inttrmtd^alt particlt silts
Prtdomuiantly ont silt or a rongt of silts with
sent inttrmiAatt suts missing.
Non-plastic lints (for idintification procidurts
sit ML bilow)
Plastic twits (for idintification procidurts
IM CL ttlow).
U*ES ON FRACTION SMALLER THAN No. 40 SIEVE SIZE
OUT STMNtTH
KRUSKING
CHAHACTEftlSTICS)
Nont to slight
MiaVum to high
Slight to mtdium
Slight to roidium
High to vtry high
Mi*um to high
OILATANCT
(REACTION
TO SHAKING I
Quick to Stow.
Nont to viry stow
Slow
Slow to noni
Nont
Nona to vary slow
TOiifHNESS
(CONSISTENCY
NCAR PLASTIC LNJITI
Nont
Mtdium
Slight
Slight to radium
High
Slight to mtditun
Rtsdily idtntilitd by cotor. odor, spang? fwf end
trtqutntly by fibrous ttiturt.
GROUP
EYU60LS
11
6W
CP
GU
CC
sw
SP
SM
SC

ML
CL
OL
UH
CH
OH
Pt
TYPICAL NAUES
Will o/odid grtvils, gravit-tond mutu/is,
hltli or no tints
Poorly grodid gronlls, grevil-|0fld miituris,
liltlt or no (mis
Silly gravils, poorly gradid gravil-sond*
silt muturts.
Cloyiy grovils, poorly graatd gravtl-sond-
cloy mixturts.
Will grodtd toads, gravtlly sondi. littlt or
no fints.
no (IMS.
Stlty sands, poorly gradtd sond-silt nuituris.
Clayiy sands.poorly grodtd sand-clay muluris.

Inorganic silts and wiry tint sandf, rock Hour, silty
or clayty fint sands with slight plasticity.
Inorganic clays of low to mi&um plasticity, grovilly
clays, sandy clays, silty clays, lion ctays
Organic silts and organic silt-ctays at tow
plasticity.
Inorganic Silts, micaetous or dtattHnactous tint
Inorgaiuc clays of high plasticity, fat clays.
Organic clays of medium TO high plasticity.
Plot and othtr highly organic soils '
INFORMATION R£QOtft£0 FOA
DESCRIBING SOILS
Gut typical nomt, intfcdt approiunatt
pireintogts of sand andgnh>il,md(
nil, angularity, surfact condition,
ond hardmss of tht coarsi grams t
local or gtotog4C namt and othir
ptrtinint dtscriptivt information.

For undislurtwd I a It odd information
on strotificalift^dia/it ol compact-
niis^iirwntatun, moisturt conditions

SMtysflftd, gravtlly ; about 20% hard,
anguioTgravtl particlts [-n maximum
SHI[ roundtd and subangular sand
grains coarst to tintj about ISX non-
plastic tints with low dry slrtnglh ;
will compacfid and moist tn ploct;
alluvial sand; ISM)

Givi typical nnmt; indicatt dtgrttand
charactir of plasticity, amount and
maximum silt at coarst grains-.color
m wit condition , odor it any, local or
giologk norm, and othtr pirlmint
discriptivt intormottoni and lymbol
in partntntsts.
For undisturbed soils add information
on ttructurt, stratification, consisttncy
in undtsturbtd and rtmoWtd statts,
moisturt onddrainagt conditions.
Clayty silt, brown-, slightly plastic ;
Small ptrctntogt of tint sand;
numtraus vtrtical root holts ; firm
and dry m plact, lots t; (ML)
LABORATORY CLASSIFICATION
CRITERIA
c
0
.1
S
1
1
s
Is
5 ** o>
*z £
!si 1°
IIL-J!
IfiSi
Hi

lii Sp
ii° j

CB - -§^- Crtotw than 4 *
Cc - g^gy Bltwttn one and 3
Not milling all gradalion rtquirt
Atltrsirg limili bllow V lint,
or PI liss than 4
Alttrbtrg limits abovtVlmt
with PI grt«ltr than 7
Cu - -{}£- Grtalir than C
Ce " b^p^; fl'*«Bft ont ond 3
Net muting all gradation rtquirtrm
Atttrfairg limits bllow V lint
or PI Itss than 4
Atttrbirg limits obovt V lint
with PI grtattr Ihm T



s» =

sSS5S^s==
\==== = ^\
LIQUID LIMIT
PLASTICITY CHART
FO* LtKMTONV CLftltlPICkTIM « fINI M»
minis for Cw
Afeovt V (wit with
PI bttwtin4andr
art bgrdtrlint costs
riqujipng uil of dual
Symbols.

nil for SW
Abovt 'A* lint with
PI bttwttn4antf7
art bordirlint casts
rt quiring ust of dual
symbols.




Nil f OIL*
                         t agyndorjf clotsifications--Soils posstssino choroctirislici of two groups art disignattd by combinations ot group symbols. For txamplt GW-6C, wtll grodtd gravil-sand muture with clay bindtr
                         • All siivt silts on this chart art us. standard.
                                                                                                                                                                     ADOPTED Br -CORP!
              Source:  U.S. Department of Interior, 1974
                                                                                     Figure 3-9.  Unified soil classification chart.

-------
                                        •   •
 skip-graded gravels, the poorly graded gravels, belong to the GP group.
 Dirty gravels are of two types:  those with nonplastic (silty) fines (GM)
 and  those with plastic  (clayey) fine  (GC).  The determination of whether
 the  fines are silty or  clayey  is made by  three manual tests for fine-
 grained  soils (described in Section 3.5.2.3).

     If  a soil is a sand, the  same steps  and criteria are used as for the
 gravels  to determine whether the soil is  a well-graded clean sand (SW),
 poorly graded clean sand (SP), sand with  silty fines (SM), or sand with
 clayey fines  (SC).

     If  a material is predominantly (more than 50 percent by weight) fine-
 grained, it is classified into one of six groups (ML, CL, OL, MH, CH, OH)
 by estimating its dilatancy (reaction to  shaking), dry strength (crushing
 characteristics), and toughness (consistency near the plastic limit) and by
 identifying it as being organic or inorganic.  (The test procedures and
 behavior of the various groups of fine-grained soils for each of the hand
 tests are shown on the  classification chart (Figure 3-8) and are described
 in Section 3.4.2.3).

     Soils typical of the various groups  are readily classified by the
 foregoing procedures.  Many natural soils, however, will have property
 characteristics of two groups because they are close to the borderline
 between  the groups either in percentages  of the various sizes or in
 plasticity characteristics.  For this substantial number of soils, border-
 line classifications are used; i.e., the  two group symbols most nearly
 describing the soil are connected by a hyphen, such as GW-GC.

     If  the percentages of gravel  and sand sizes in a coarse-grained soil
 are nearly equal, the classification procedure is to assume the soil is a
 gravel and then continue the classification procedure using the chart until
 the final soil group, say GC, is reached.  Since it could have been assumed
 that the soil is a sand, the correct field classification is GC-SC because
 the criteria for the gravel  and sand subgroups are identical.  Similarly,
within the gravel or sand groupings, borderline classifications such as
GW-GP, GM-GC, GW-GM, SW-SP,  SM-SC, and SW-SM can occur.

     Proper classification of a soil near the borderline between coarse-
grained and fine-grained soils is  accomplished by classifying it first as a
coarse-grained soil  and then as a  fine-grained soil.  Such classifications
as SM-ML and SC-CL are common.

     Within the fine-grained division, borderline classifications can occur
between  low-liquid-limit soils and high-liquid-limit soils as well  as between
silty and clayey materials in the  same range of liquid limits.  For example,
one may find ML-MH,  CL-CH,  and OL-OH soils; ML-CL,  ML-OL, and CL-OL soils;
and MH-CH,  MH-OH, and CH-OH  soils.

3.4.2.2  Laboratory Classification--
     Although most classifications of soil will  be  done visually and by
simple hand tests, the USCS  has provided for precise delineation of the
                                    3-17

-------
 soil groups by gradation analyses and Atterberg  limits  tests  in  the  labora-
 tory.  Laboratory classifications are often  performed on  representative
 samples of so'ils which are to be subjected to  extensive testing  for  shear
 strength, compressibility, and permeability.  They  can  also be used  to
 advantage in training the field classifier of  soils to  improve his ability
 to estimate percentages and degrees  of plasticity.

      The grain-size curve is used to classify  the soil  as being  coarse-
 grained or fine-grained and, if coarse-grained,  into gravel or sand  using
 the 50-percent criterion.  Within the gravel or  sand groupings,  soils
 containing less than 5 percent finer than the  No. 200 sieve size are con-
 sidered "clean" and are then classified as well-graded  or poorly graded by
 their coefficients of uniformity and of curvature.   In  order  for a clean
 gravel  to be well-graded (GW), it must have  both a  coefficient of uniformity,
 Cu,  greater than 4 and a coefficient of curvature,  Cc,  between 1 and 3;
 otherwise, it is classified as a poorly graded gravel (GP).   A clean sand
 having  both Cu greater than 6 and Cc between 1 and  3 is in the SW group;
 otherwise, it is a poorly graded sand (SP).

      "Dirty" gravels or sands are those containing  more than  12 percent
 fines,  and they are classified as either siHy or clayey by results of
 their Atterberg limits tests as plotted on the plasticity chart shown in
 Figure  3-8.  Silty fines are those that have a PI less  than 4 or that plot
 below the "A" line.  Clayey fines are those  that have a PI greater than 7
 and  that plot above the "A" line.       ;

      Coarse-grained soils containing between 5 and  12 percent fines are
 borderline cases between the clean and dirty gravels or sands (i.e., GS,
 GP,  SW,  SP, GM,  GC, SM,  and SC).   Similarly, borderline cases may occur
 in dirty gravels and dirty sands  where the PI  is between 4 and 7 (GM-GC,
 SM-SC).   It is theoretically possible,  therefore, to have a borderline
 case of  a borderline case;  but this  refinement is not used, and the rule
 for  correct classification is to  favor the nonplastic one.  For example,
 a gravel  with 10 percent fines,  a Cu of 20, a Cc of 2.0, and a plasticity
 index of 6, would be classified GW-GM rather than GW-GC.

      If  a soil  is determined to  be fine-grained by  using the grain-size
 curve,  it is further classified  into  one of the six groups by plotting the
 results  of Atterberg limits  tests  on  the plasticity otiart, with attention
 being given to the organic  content.   Inorganic, fine-grained soils with
 a plasticity index greater  than 7  and  above the "A" line are CL or CH,
 depending  on  whether their  liquid  limits are less than 50 percent or more
 than  50  percent,  respectively.  Similarly, inorganic, fine-grained soils with
 a plasticity index less  than  4  or  below the "A" line are ML or MH, depending
 on whether  their liquid  limits are less than or more than 50 percent, respec-
 tively.   Fine-grained  soils  that  fall above the "A" line but that have a
 plasticity  index  between 4 and 7 are classified as ML-CL.

     Soils  below  the  "A"  line that are definitely organic are  classified as
OL if they  have  liquid limits less than 50 percent and as  OH if the liquid
 limits are  above  50 percent.  Organic silts  and clays are  usually distin-
guished from  inorganic silts, which have the  same position on  the plasticity
                                    3-18

-------
 chart,  by odor and  by  color.   Howey_er, when the organic content is doubtful.,
 the material  can  be oven  dried,  remixed with water, and retested for liquid
 limits.  The "plasticity of  fine-grained organic soils is greatly reduced
 on  oven drying due  to  irreversible changes in the organic colloids.  Oven
 drying  also affects the liquid limit of inorganic soils but to a much smaller
 degree.  A reduction in liquid limit after oven drying to a value less than
 three-fourths  of  the liquid limit before oven drying is considered positive
 identification of organic soils.

 3.4.2.3  Field Identification  Procedures for Fine-Grained Soils or
          Fractions—
      These procedures  are to be performed on the minus No. 40 sieve size
 particles (approximately  1/64  inch).  For field classification purposes,
 screening is not  intended;  simply remove by hand the coarse particles that
 interfere with the  tests.

      3.4.2.3.1 Dilatancy (Reaction to Shaking)—After removing particles
 larger  than No. 40  sieve  size, prepare a pat of moist soil with a volume of
 about one-half cubic inch.  Add enough water if necessary to make the soil
 soft but  not sticky.

      Place the pat  in  the open palm of one hand and shake horizontally,
 striking  vigorously against the other hand several times.  A positive
 reaction  consists of the  appearance of water on the surface of the pat,
 which changes  to  a  livery consistency and becomes glossy.  When the sample
 is  squeezed between  the fingers, the water and gloss disappear from the
 surface,  the pat  stiffens, and finally it cracks or crumbles.  The rapidity
 of  appearance  of water during  shaking and of its disappearance during
 squeezing  assist  in  identifying the character of the fines in a soil.

      Very  fine clean sands give the quickest and most distinct reaction,
 whereas a  plastic clay has no  reaction.  Inorganic silts, such as a typical
 rock  flour, show a moderately quick reaction.

      3.4.2.3.2  Dry Strength (Crushing Characteristics)—After removing
 particles  larger than No.  40 sieve size,  mold a pat of soil  to the
 consistency of putty, adding water if necessary.  Allow the pat to dry
 completely by oven,  sun,  or air drying, and then test its strength by
 breaking and crumbling between the fingers.  This strength is a measure
 of  the character and quantity of the colloidal  fraction  contained in the
 soil.  The dry strength increases with increasing plasticity.

      High dry strength is  characteristic  for clays of the CH group.   A
 typical  inorganic silt possesses only very slight dry strength.  Silty
 fine  sands and silts have  about the same  slight dry strength but can be
distinguished by the feel  when powdering  the dried specimen.  Fine sand
feels gritty,  whereas a typical silt has  the smooth feel  of flour.

     3.4.2.3.3  Toughness  (Consistency Near Plastic Limit)—After removal
of particles  larger  than  the No. 40 sieve  size,  a specimen of soil  about
                                    3-19

-------
 one-half cubic inch in size is molded  to :the  consistency of putty.  If too
 dry,  water must be added and,  if  sticky, the  specimen should be spread out
 1n a  thin layer and allowed to lose  some moisture by evaporation.  Then the
 specimen is rolled out by hand on a  smooth  surface or between the palms into
 a thread about one-eighth inch in diameter.   The thread is then folded and
 repelled repeatedly.  During this manipulation the moisture content is
 gradually reduced and  the speciment  stiffens, finally loses its plasticity,
 and crumbles when the  plastic  limit  is reached.

      After the thread  crumbles, the  pieces  should be lumped together and a
 slight  kneading action continued  until  the  lump crumbles.

      The tougher the thread near  the plastic  limit and the stiffer the lump
 when  it finally crumbles, the more potent is  the colloidal clay fraction in
 the soil.  Weakness of the thread at the plastic limit and quick loss of
 coherence of the lump  below the plastic limit indicate either inorganic clay
 of low  plasticity or materials such  as kaolin-type clays and organic clays
 that  occur below the A-line.

      Highly organic clays have a  very  weak  and spongy feel at the plastic
 limit.

 3.5  COMPACTION

      Soil  compaction is  the rapid application of mechanical force to a soil
 to increase its density.   In the  construction of clay liners, compaction is
 done  to decrease the permeability of the liner material.  Compactive effort
 is the  term used to describe the  amount of mechanical energy applied to the
 soil.   The units of compactive effort  are foot pounds of energy per cubic
 foot  of soil  (ft-lb f/ft3)  or joules per cubic meter (J/m3).

 3.5.1   Fundamentals of Compaction

      In a 1933  series  of  publications  on soil compaction, R. R. Proctor de-
 scribed a laboratory procedure that, in its modern form, has become one of
 the standard methods for  determining the moisture, dry density, and compac-
 tive effort relationship  of compacted  soils (Proctor, 1933).  In the Proctor
 compaction  test,  soil  densification  is  achieved through the application of
 a  standard  dynamic  impact  (compactive  effort).  A standardized procedure
 has been  adopted  and described in ASTM  test method D698-78 (ASTM,  1984).
 The test  is performed  by  placing  a layer (lift)  of test soil, approximately
 2  Inches  thick,  in  a cylindrical   compaction mold and dropping a 5.5-pound
weight  onto its  surface 25  times  from a height of 1 foot.  This procedure is
 repeated  for two  subsequent  lifts, resulting in  a compacted sample with three
 lifts.  The dry density of  the compacted sample  is then determined.  This
procedure  is repeated  several times on  samples of the same soil  at different
moisture contents.  When  the testing is completed,  the water contents of the
samples are plotted against  the dry densities achieved after compaction.
This exercise produces a  compaction curve (also  called a moisture  density
curve) as illustrated  in Figure 3-10.
                                     3-20

-------
   19.0

   18.0
 c



Q
   17.5
                                      ine of Optimums
                  Optimum Water

                  Content
                               J	L_J
                               10      12       14

                               Water Content, w (%)
      Source: Lambe, 1955
16      18
                                                                            0.41
                                                                            0.43
                        to
                        CC

                   0.46 2
                        o
                                                                           0.49
                                                                           0.52
     Figure 3-10.  typical soil compaction curve illustrating maximum dry density
                         and optimum water content.
                                    3-21

-------
     The Illustration presents only one curve achieved with one compactive
effort.  Changing the compactive effort will produce similar curves with
different maximum dry densities and optimum water contents (optimum water
content is the water content corresponding to the maximum dry density
achieved in the test).  Increasing the compactive effort increases the
maximum dry density and decreases the optimum moisture content.  A typical
series of compaction- curves for a single soil at different compactive efforts
1s presented in Figure 3-11.  Note that changing the compactive effort also
can change the shape of the compaction curve.

     The most important feature on the compaction curve is its peak, which
represents the maximum dry density that can be achieved with a given compac-
tive effort.  As stated above, the moisture content corresponding to this
peak is called the optimum water content.  The line of optimums connects the
maximum densities and optimum water contents of compaction curves produced by
different compactive efforts applied to samples of the same soil.  The line
of optimums runs nearly parallel to the zero air voids line (also called the
100-percent saturation line), which represents the saturated water contents
for different dry densities of a given soil.

     The compaction curves in Figure 3-11 clearly illustrate that, for a
given soil, compacted density is a function of soil moisture content and
compactive effort.  Care must be taken in compaction tests to ensure that
moisture is evenly distributed through the soil mass.  Winterkorn and Fang
(1975) point out that:

     ... to avoid irregular and meaningless moisture density curves
     in laboratory and field tests on highly cohesive soils, it is
     imperative that the moisture be evenly distributed throughout the
     secondary soil aggregates.  This may take from 1 to 7 days in the
     case of highly cohesive soils to which water is added in the dry
     condition.

     The Interpretation of compaction test results is not always straight-
forward.  Winterkorn and Fang (1975) point out:

     . . . even properly performed tests may not yield the generally
     expected paraboloid curves.  Andrews, et al. (1967) found two
     optimum moisture contents for the compaction of ila-bentonlte,
     one at 100 percent H20 yielding 73 lb/ft3 and one at 50 per-
     cent FLO yielding 65 lb/ft3.  Lee and Suedkamp (1972) reported the
     existence of four types of moisture-density curves [as shown
     in Figure 3-12].  They are (A) single-peak, (B) 1'peak, (C) double
     peak, and (D) oddly stiaped with no distinct optimum moisture con-
     tent.  They related the different types to the liquid limit ranges
     as follows:  LL<30, double and 1-1/2 peaks; LL 30 to 70, typical
     single peak; LL>70, peaked and oddly shaped curves.

These unusual  curves are not likely to be encountered with clays suitable
for liners (Mitchell, J. K., 1985, Dept. of Civil  Engineering, University
of California,  Berkeley, personal  communication).
                                     3-22

-------
£
•«••.
Z
JC
•^
  •
I-
e
o
     19
     18
     17
Z   16
2
      15
     14
               10            15             20

                        WATER  CONTENT (%)
                                                           25
lo.
1
2
3
4
Layers
5
5
5
3
Blows per
Layers
55
26
12
25
Hammer
Mass
4.54kg
5.54
4.54
2.50
                                             Hammer
                                              Drop
                                             457mm (mod.AASHO)
                                             457
                                             457    (std. AASHO)
                                             305
     Source: Lambe and Whitman, 1979
          Rgure 3-11. Compaction curves for different compactive efforts
                            applied to a siity ciay.
                                3-23

-------
                    Type A
                            \
                                 \
                     TypeC
 Type B
TypeD
                                                          A
           After Winterkorn and Fang, 1975




Figure 3-12.  Four types of compaction curves found from laboratory investigation.
                                  3-24

-------
 3.5.2   Compaction  and  Permeability

     During  fhstallation  of  a  clay  liner,  compaction  is controlled by
 measuring  density  and  moisture content  in  each  lift.  However, these
 measurements by  themselves are meaningless unless they ultimately can be
 related back to  the  permeability.   (See  Figures 3-13  and 3-14.)

     Mitchell, Hooper,  and Campanella  (1965)  investigated the relationship
 between these variables and  found that,  at a  given density, permeability
 was  very sensitive to  variations in  the  molding water (moisture) content.
 They performed a series of compaction  tests on a silty clay, samples of
 which were kneaded to  constant density at  different water contents.  When
 permeability tests were performed,  the permeability increased slightly
 between 12 and 18  percent molding water  content but then decreased by
 around  3 orders  of magnitude as the  water  content increased from 18 to
 19.5 percent.  The decreased permeability  corresponded to compaction per-
 formed  at  water  contents  on  the wet  side of optimum;  minimum permeability
 occurred on  the  "wet-of-optimum" side of the  compaction curve and not at the
 maximum density.   Mitchell et  al. (1965) also found that, in the laboratory,,
 lower permeabilities are  achieved with kneading compaction than with static
 compaction.   These phenomena are discussed in Chapter 2 of this report.

     This  discussion gives rise to the following conclusion:  to achieve a
 specified  permeability, soil moisture, compactive effort, and dry density
 must be carefully  measured and  controlled.

 3.6  FIELD MEASUREMENT  OF DENSITY AND MOISTURE CONTENT

     Controlling clay  compaction in  the  field so that a specified per-
 meability  is achieved  is  done  through control of the moisture content
 and  density.  Methods  for measuring moisture content  are summarized in
 Appendix A,  Methods  1  through 7.  Field  density or unit weight measurements
 are  summarized in  Methods 8  through  13.  The following text discusses the
 more commonly used techniques  in more detail.

 3.6.1   Traditional Methods

 3.6.1.1  Density--
     Two traditional  methods are used for measuring density in the field.  In
 one  type of  test, a small hole  is dug in the compacted fill  and the excavated
material is  saved and weighed.  The volume of the hole is measured by filling
 it with  sand or  liquid with  a device that measures the amount of material
 required to  fill  the hole.   The sand cone and rubber balloon methods are
 examples of  this category of test (Appendix A, Methods 10 and 11).

     Another technique  is to drive a hollow cylinder  into the fill, remove a
 core, trim it to a known  volume, and then determine its weight.  This drive-
 cylinder method  (Appendix A, Method 12) and the sand cone and rubber balloon
methods  take time because the sample must be oven dried before the dry den-
 sity can be determined.
                                    3-25

-------
   0  1x10
   §  1X10-7
   Q
   Z
   O
   O

   O


   ^  1x10*8
   ce
   a
      1x10
           -9
 r    i

12
                 14
                                    i    r    r

                                   10       13
                                        i     r
   co
   >
   ac
   a
114



110



108
                     Kneading
                 compaction curva ''••.
                          \
20
                          Line of optimums
                      13       15       17       19

                     MOLDING, WATER CONTENT (%)
 Source: Mitchell, 1975
Figure 3-13. Permeability as a function of molding water content for samples
    of silty clay prepared to constant density by kneading compaction.
                          3-26

-------
   1x10
       -5
*  5x10
S
o
       -6
       -6
>  1x10
§  5X10-7
Q
O        7
3  1x10  7


ff  5x10"8
Q
_ O
             Optimum water content
                _L
                               Static compaction
                  Kneading compaction
                I	|	I     !      |
                15    17   19   21    23   25   27

                 MOLDING WATER  CONTENT  (%)
      108  -
>
H-
35 -.
Z ^"9
at c
Q ^
> S
cr
Q
106
104



102
—
° ^-^•°*»^
X^^ V Npv
/ ° °N
V
X
Y*
      100  -
                      I
                           I
               15    17   19   21    23   25   27

                  MOLDING WATER CONTENT <%)


          o   Kneading compaction   1' x  2.8" 0 mold

          •   Kneading compaction   3.5*  x 1.4" 0 mold

          v   Static compaction  1" x 2.8" 0 mold
 Source: Mitchell, 1976
         Rgure 3-14. Influence of the method of compaction
                  on the permeability of silty clay.
                        3-27

-------
 3.6.2  Nuclear Methods

      Nuclear "gauges  offer  a  faster and more convenient method for measuring
 field density  and moisture content than those methods described in Section
 3.6.1 and  are  presently widely  used  for earthwork compaction quality con-
 trol.  Nuclear gauges are  designed to give very rapid measurements of density
 and moisture content.

 3.6.2.1 Nuclear Density Gauge—        :
      Nuclear density gauges  consist  of a source of gamma rays, typically
 Cs-137 (0.662  Mev),  and a  detector (or nest of detectors) separated hori-
 zontally from  the source.  The  gauges are used in two modes:  a "back-
 scattering"  mode in  which  the gamma  rays are directed, by collimation,
 downward into  the soil where they are scattered with some fraction reaching
 the detector and a transmission mode in which the source is lowered into a
 hole  in the  soil (2  to 12  inches deep) and the number of gamma rays pene-
 trating the  soil to  reach  the detector on the surface is recorded.  In
 the range  of densities of  interest (70 to 160 lb/ft3), the gamma rays
 that  reach the  detector decrease with increasing soil density.

      Gamma rays interact with the electrons that are a part of the atoms
making  up  the  soil.  Two types  of interactions are exploited for measuring
density.   The  primary interaction is Compton scattering wherein the gamma
 ray is  deflected (scattered) by an electron and continues in a different
direction  at a  reduced energy.  For the elements found in soil, Compton
scattering is  the predominant reaction in the energy range above 100 keV.
The second interaction is  photoelectric absorption wherein the gamma ray
gives  up all its energy to an electron and is removed from the beam.  The
frequency  of this interaction becomes greater as the gamma ray energy
decreases  from  100 keV.  The probability of this reaction also increases
with  the atomic number of  the element.  :

      The relative frequency  of these two interactions is a function of the
soil's  chemical composition.  The effects can best be illustrated by first
considering  the predominant  reaction, Compton scattering, and then the
modification introduced by photoelectric absorption.

      The Compton scattering  cross section, i.e., the probability of a
scattering event, is proportional to the electron den-sity of the medium.
This  1s given by:


                           De = Dm N = W1  VAi                         <3-n)

where                                   ;

     Dm - mass density of the medium

     N  - Avogadro's number

     V/i - weight fraction of element
                                    3-28

-------
     Zj = atomic number of element

     A-J = atomic weight of element.

Thus, the electron density is related to the mass density by the factor
Z/A of the medium.  The Z/A of the various soil  components is given  in
Table 3-3.  Except for Fe2<33 (Z/A - 0:476), the  major soil components
have Z/A values that fall  within the range of 0.489 to 0.500.  Thus,  if
Compton scattering alone were responsible for the attenuation of the  gamma
rays, the mass densities would be within a few tenths of a percent of the
instrument gauge indications except for soils containing appreciable  amounts
of F6203.  Water also has a measurable effect on nuclear density measure-
ments.  Because of its high Z/A, its electron density (per gram) is
high.  As a result, a dry soil of a given density will produce a slightly
lower nuclear gauge density reading than a wet soil of the same mass  den-
sity.  The different readings are a consequence  of the difference in  the Z/A
of the two soils (Table 3-3; clay and clay + 10  percent H20).

     Thus, with respect to the Compton scattering component, the gauge  will
read iron-rich soils lower than their actual density and damp soils  somewhat
higher than their actual density.

     The cross section for the photoelectric effect interaction of gamma
rays with electrons is experimentally determined to be about proportional
to Z^/A.  Thus, this effect becomes increasingly important for higher Z
elements such as calcium, which has a Z of 20.  The other major earth
elements—oxygen, silicon, and aluminum—have relatively low Z values
(8, 14, and 13, respectively), so the photoelectric effect for these is
less than for calcium.  The consequence is that more gamma rays are  absorbed
per unit of electron density in calcareous soils than in noncalcareous  soils
and the nuclear gauge density reading is therefore higher than the actual
density.

     To minimize this effect, ASTM Standard 2922 (ASTM, 1984) requires
that nuclear density gauge calibration blocks include two that bracket
the attenuation coefficient of soils and suggests limestone and granite.
The calibration curve is adjusted to fall halfway between the limestone
and granite data.  As a result of this compromise, highly calcareous
soils will read 2 to 3 lb/ft3 high and highly siliceous soils will read
2 to 3 lb/ft3 low when measurements are made in the transmission mode.
This effect is exaggerated further in the backscattering mode, where the
photoelectric effect is greater.  In the backscattering mode, highly
calcareous soils will read 3 to 4 lb/ft3 high and highly siliceous
soils will read 3 to 4 lb/ft3 low.

     Although iron is not a major component of the earth's crust,  some  soils
contain sufficient iron to affect the reading of a nuclear density gauge.
Biotite mica, other iron silicates,  and iron oxides (e.g.,  goethite and
hematite) are some of the more common iron-containing minerals in  soils;
nuclear density measurements in soils containing iron minerals should be  made
with care.  Because the Z of iron is 26,  the photoelectric effect  becomes
quite important and the gauge will  indicate a density higher than  the actual
value when calibrated according to ASTM Standard 2922.
                                    3-29

-------
TABLE 3-3.  Z/A OF VARIOUS SOIL COMPONENTS
   Components
ZI/AI
Silica  (Si02)
Feldspar  (KAlSi308)
Lime  (CaC03)
Alumina (A1203)
Soda  (Na203)
Magnesia  (MgO)
Clay  (Al6Si2Oi3)
Clay + 10% H20
Fe203
H20
0.500
0.495
0.499
0.490
0.489
0.495
0.496
0.502
0.476
0.555
                  3-30

-------
     A method for overcoming the chemical composition error is to calibrate
the gauge against a series of sand cone tests performed on the soil of
interest.  TKe precision of a series of sand cone tests is poorer than the
precision of nuclear gauge tests, but the accuracy is generally better if
the sand cone tests are done carefully.  The ratio of the sand cone density
to the nuclear density may then be applied to the nuclear gauge reading to
achieve the corrected density.

     When used in the backscattering mode, "surface roughness" may cause
inaccurate density measurements.  If the soil surface is not a perfect plane,
air voids are formed between the gauge and the soil, reducing the density of
the volume beneath the gauge.  A 50-mil air gap will result in a density
reading that is about 4 lb/ft3 low.

     The uniformity of the soil density is also important in the back-
scattering mode.  About 60 percent of the gauge response is from the top
inch of soil, 25 percent from the second inch, and 10 percent from the third
inch.  Thus, while a gauge may be quoted as having 95 percent of its response
from a 3-inch depth, the response versus depth in this region is in no way
uniform.  In summary:

     t  Nuclear density gauges are factory calibrated to give compromised
        measurements in two soil extremes.  In highly calcareous dry
        soils, the gauge will read high by 2 to 3 lb/ft3 at 120 lb/ft3
        in the transmission mode and in highly siliceous soils low by 2
        to 3 lb/ft3.  In the backscattering mode, the gauges are 3 to
        4 lb/ft3 high and low, respectively, at 120 lb/ft3.  The gauge
        would be expected to read properly in clays with up to 10 to
        12 percent water content if no high Z elements such as calcium
        and iron are present in appreciable quantities.  Nuclear gauges
        will read iron-rich soils lower than their actual density and
        damp soils somewhat higher than their actual density.

     •  In the backscattering mode, the nuclear gauge is sensitive to any
        density variations in the upper 3 inches of soil and to the flatness
        of the soil surface upon which the gauge rests.

     •  It is customary to calibrate the nuclear gauge against a series of
        sand cone tests to overcome chemical composition problems in the
        field.  A gauge reading (preferably in the transmission mode) is
        taken, and then a sand cone test is made on the same volume measured
        by the gauge.  The average of the ratio of the sand cone test to the
        gauge reading for a series of tests then becomes the correction
        factor to be applied to the gauge reading.  This correction factor
        will apply as long as the chemical composition of the soil  does not
        change appreciably.

3.6.2.2  Nuclear Moisture Gauge--
     Nuclear moisture gauges consist of a source of fast neutrons (usually
an americium-beryllium source) and a slow neutron detector mounted as close
to one another as possible.  The principle of operation is that of neutron
                                    3-31

-------
 moderation, i.e., the slowing down of neutrons caused by elastic  scattering
 from the nucl-ei in the scattering medium.   Hydrogen  is an excellent moderator
 because its nuclear mass is the same as the mass  of  a neutron  and each  inter-
 action with hydrogen results in a major energy loss  to the neutron.  On the
 average, about 19 collisions with hydrogen nuclei  will  thermalize the neu-
 tron, i.e., reduce its energy to that of! the surrounding nuclei.   The other-
 elements in the earth's crust are not nearly as effective—oxygen requires
 about 158 collisions on the average and silicon 273.   The readings obtained
 with a nuclear moisture gauge are essentially independent of the  density of
 the medium because,  except for hydrogen,  the medium  is  nearly  transparent to
 the neutrons.

      By using  a slow neutron detector,  i.e.,  one responsive only  to thermal
 neutrons,  one  can measure  the number of neutrons thermalized, which is a
 function of the number of  hydrogen  atoms in  the medium.   In inorganic soils,
 water provides the bulk of the hydrogen and  thus the water content can be
 measured.   The greater the water content,  the  greater the number  of neutrons
 thermalized.

      Because of the  system's geometry,  the gauge  is most sensitive to the
 hydrogen content in  the immediate vicinity of the  detector.  At low moisture
 contents,  the  neutron moves further from the source-detector position before
 it  has undergone enough collisions  to thermalize  it and  is far enough from
 the detector that the probability of returning to  the detector is low.  On
 the other  hand, a high moisture content will  permit thermalization much
 closer to  the  detector. This leads to  the conclusion  that the active volume
 of  measurement is a  function of the moisture content.

      Experimentally  determined depths of measurement  for a typical neutron
 gauge give the following expression for the  depth where  95 percent of the
 detected interactions will  occur:

                         D (inches)  = 11 - 0.17 MC                     (3.12)

where

      MC  *  moisture content in  pounds  of water  per cubic  foot of soil.

      When  Equation (3.12)  is  applied  to a  hypothetical case, if a soil
sample has a density  of 120  lb/ft3  and moisture content  of 12 percent,  it
contains 14.4  pounds  of water  per cubic foot and the sensitive depth is
8.5 inches.  Note, however,  that  if the moisture is nonuniform, the gauge
response will  be  biased toward  the moisture  content near the detector.

     Another reaction  can modify the gauge reading when certain soil  elements
are present.  Aside from the moderation interactions, certain elements  have
a high probability of absorbing a neutron.  The only ones normally found in
soil are iron and chlorine, the latter where saline soils exist*   Thus,
coastal soils may contain sufficient chlorine to be significant and iron
                                    3-32

-------
 oxide  or  silicate  contents  of  35  to 40 percent will cause errors.  In
 summary:
                                fc. , £-'' '     '•  ft* -*
     • Neutron gauges are  useful for measuring the moisture content of
        inorganic  soils  of  uniform water  content.  Although the sensitive
        depth  of measurement may  normally be 6 to 8 inches, the response
        is biased  toward the moisture content near the detector.

     9 If hydrogen-containing materials  (including clay minerals) other than
        water  are  present,  the gauge will respond to this hydrogen.  Coastal
        soils  may  have sufficient chlorine content to interfere, and high
        iron oxide or silicate content will influence the moisture
        measurement.

     » In order to compensate for the soil compositions that may affect
        the neutron response,  it  is customary to calibrate the gauge against
        tests  on the oven-dry  soil.  This is generally done with the soil
        samples extracted for  the density calibration.

 3.6.2.3  Modern Nuclear  Density and Moisture Gauges--
     Current nuclear gauges contain both  density and moisture-measuring
 components.  A key pad,  display unit, and microprocessor enable various
 correction factors to be entered  into the gauge for particular soils.
 Operating manuals  provide complete instructions for the use of the gauge
 under  various  conditions.   In addition, gauge manufacturers provide training
 seminars on the proper use  of  their gauges, including safety considerations",

 3.7  TESTING FOR SHEAR STRENGTH

     The shear strength  of  a son must be known before an earthen structure
 can be designed and built with assurance  that the slopes will not fail (see
 Chapter 5).

     A soil mass may be  considered to be a compressible skeleton of solid
 particles.  In saturated soils the void spaces are completely filled with
 water; in partially saturated soils the void spaces are filled with both
 water  and air.  Shear stresses are carried only by the skeleton of solid
 particles, whereas the normal stress on any plane is carried by both the
 solid  particles and the  pore water.                 -

     The development of  shear  in a saturated cohesive (clay) soil  is com-
 plex because an applied  load is initially supported by the stress in the
 pore water (neutral stress) and is not immediately transmitted to the soil
 structure.  Because of the very low permeability of clays, neutral stresses
 are transmitted to the soil structure very slowly, sometimes requiring months
 or years before the soil  structure feels the full  stress increase.  Another
 complicating factor is the attractive and repulsive interaction between the
 clay particles (Sowers and Sowers, 1971).

     The triaxial   compression test is commonly used to measure the shear
 strength of a soil  under controlled drainage conditions.  A triaxial  com-
pression chamber consists primarily of a head plate and a base plate
 separated by a transparent plastic cylinder (Figure 3-15).  In the basic
                                    3-33

-------
     -Dial Indicator
                                                                        Pressure Gage
                                                                                 Pressure
                                                                                 Regulator
                                                                                    *"""?
                                                                                Air Pressure Line
                                                                Chamber
                                                                Pressure
                                                                Reservoir
Source: U.S. Department of the Army, 1970

     Rgure 3-15. Schematic diagram of triaxiai compression apparatus for Q test.
                                   3-34

-------
triaxial test, a cylindrical specimen of soil, encased in a rubber membrane,
is placed  in the chamber.  Connections at the ends of the soil specimen
permit contra!led drainage of pore water.  The chamber is filled with water
and pressurized, thereby establishing a confining pressure on the specimen.
The specimen is then loaded axially to the point of failure.  The axially
applied stress is called the "deviator stress."  In general, a minimum of
three specimens, each under a different confining pressure, are tested to
establish  the relation between shear strength and normal  stress (U.S.
Department of the Army, 1970).

     Three types of triaxial compression tests have been  developed to measure
the shear  strength of clays.  The tests differ in the drainage conditions
established for the sample and shear stress application rate.  These tests
are:

     «  Consolidated-Drained (CD) Test or Slow (S) Test—The desired con-
        fining stress is applied to the specimen and drainage is allowed
        until 100-percent consolidation is achieved.  The rate of applied
        shear stress is slow enough that essentially no change in the initial
        pore pressure occurs.

     «  Consolidated-Undrained (CU) Test or Consolidated  Quick (R) Test—As
        in the CD test above, the derived confining stress is applied to the
        specimen and drainage is allowed until 100-percent consolidation is
        achieved.  No drainage is allowed during the application of shear
        stress and the specimen remains at a constant volume and water
        content.

     9  Unconsolidated-Undrained (UU)  Test or Quick (Q) Test—No drainage
        is allowed during application  of the confining stress or during
        application of shear stress.  The unconfined compression test is a
        special  case of the UU test with the confining stress equal  to zero.
        The principal  stress difference at failure is called the unconfined
        compressive strength.

Detailed discussion of the protocols for shear strength testing and interpre-
tation of the test results are beyond  the scope of this document.  The reader
is referred to the U.S. Department of  Interior (1974) and U.S. Department of
the Army (1970)  for test protocols.  Explanations of<*he  theory and interpre-
tation of the test can be found in geotechnical  engineering texts such as
Lambe and Whitman (1979) and Holtz and Kovacs (1981).

3.8  HYDRAULIC CONDUCTIVITY TESTING

     Laboratory and field tests to quantify the hydraulic conductivity
(permeability)  of low-porostty soils to water have been used for years.
Historically, information on permeability has been required to evaluate
seepage characteristics of soils in a  variety of applications ranging from
earthen dams to  septic tank drainage fields.  These same  test procedures
have been adapted,  with some modifications,  to evaluate the performance of
compacted clay liners.
                                    3-35

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      Hydraulic conductivity testing of clay liner material  is  used  for
 facility design, for construction quality control  (CQC),  and for  clay/
 chemical compatibility evaluation.  CQC tests  are conducted to ensure
 that the hydraulic conductivity of an installed  clay  liner  meets  the
 performance specification.  A compatibility test is conducted  to  determine
 if a particular soil's permeability is altered by a liquid  waste  with which
 it might come in contact in a specific application.   Chemical  compatibility
 is discussed, at length, in Chapter 4.

      Theoretical knowledge has not yet reached the stage  of providing reli-
 able estimates of permeability.  Thus,, field and laboratory measurements are
 needed.   Standard procedures, however, have not  been  adopted for  permeability
 testing  related to hazardous waste containment.

      Effective porosity, pore-size distribution,  fluid viscosity, and fluid
 density  determine the permeability of clay soils to fluids.  Any  action that
 affects  the soil's fabric may affect the effective porosity and,  in turn,
 the permeability.  Such modification of the soil  fabric might  be  physical,
 as with  soil  compaction, or chemical,  through  the  various processes that can
 occur when  a chemical  waste interacts  with the clay (see Chapter  4).

      In  general, the procedure for measuring the permeability  of  a compacted
 soil  is  to  enclose the sample tightly  in a cylinder (permeameter) and then to
 pass  the liquid (permeant),  usually under pressure, through the sample.  The
 pressure differential  across the  sample is expressed  in terms  of  hydraulic
 gradient (a dimensionless quantity)  that is the  head  loss across  the sample
 divided  by  the sample's height.   The gradient  can  be  controlled by super-
 imposing air pressure  above  the permeant supplied  to  the sample and by
 regulating  the pressure applied at the effluent  end of the  column.  High
 hydraulic gradients  reduce  testing time by forcing permeant through the
 sample at a greater  rate than  could  be achieved with  low gradients; however,
 the amount  of gradient may  influence the test  results.

 3.8.1  Darcy's  Law

     Hydraulic  conductivity  (K) or permeability  is a measure of how rapidly
 a  permeant  fluid  can move through  porous  soils under a hydraulic gradient.
 Quantitatively,  K  is defined as the  constant of proportionality in Darcy's
 law (Equation 3.14).   To  calculate K for  a  given soil* sample,  one must be
 able to measure  the volumetric flow  rate  through the sample, the cross-
 sectional area  of  the  sample perpendicular  to  the direction of fluid flow,
 and the  hydraulic  gradient across  the  sample.

     The  flow of  liquids  through clay  has  been found to obey Darcy's Law,
which states that  the  volumetric flow  rate  of water through a  porous medium
 is proportional  to the  cross-sectional area of the medium and  to the hydrau-
 lic gradient impressed  across  it.  The constant of proportionality (K)  is
defined as  the  soil's  hydraulic conductivity.  This is expressed in
 Equation  (3-13):

                                     Q = KAh/L                         (3.13)
                                    3-36 ;

-------
 where

      Q = volumetric flow rate, em3/s

      K = hydraulic conductivity (permeability),  cm/s

      A = cross-sectional  area of specimen,  cm2

      h = change in hydraulic head (head  loss)  across  the  specimen,  cm

      L - length of sample,  cm.

      Total  or hydraulic head (h)  is  the  combination of  the elevation dif-
 ference between the in-fTow and the  out-flow fluid levels and any applied
 pressure or vacuum expressed as an equivalent  height  of water column.
 Note that h/L is the hydraulic gradient.  Also note that although K appears
 to have the dimensions  of a velocity,  this  is  an artifact due to the can-
 cellation of units.  The  true dimensions are cm3/cm2  s  (i.e., volume
 per unit area per unit  time).  Darcy's Law  assumes a  direct proportionality
 between the hydraulic gradient and the flow rate.

      When fluids other  than water are  used, the permeability as defined
 above will  be different if  the viscosity and/or density of the fluid differs
 from that of water.  It is  convenient  to define an intrinsic permeability
 coefficient that considers  these  two parameters.  The equation for intrinsic
 permeability is:
                                                                       (3.14)

where

     k =  intrinsic permeability, cm2

     K =  permeability, cm/s

     M =  dynamic viscosity, g/cm s

     p =  density, g/cm3
                                                     *
     g =  gravitational constant, cm/s2.

     A fluid's viscosity is a measure of its resistance to flow while its
density measures the degree to which gravity influences its flow behavior.
For liquids other than water, these two factors influence the fluid conduc-
tivity in a porous media.

     Knowing the hydraulic conductivity of a clay and the hydraulic con-
ditions at the top and bottom of the liner enables one to calculate the
volumetric flow rate (Q)  through a saturated, homogeneous liner composed
                                    3-37

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of that clay.  Given a liner area (A) of 20,000 ft2 (about half an
acre), a liner thickness of 3 ft (L), 1 ft of water over the liner making
h equal 4  (1 ft water + 3 ft of saturated liner), and a permeability
(K) of 10-' cm/s (2.88 x 10"4 ft/d), the volumetric flow rate from
Equation (3.13) will be:

             Q = KAh/L                   i

             Q = (2.88 x 10-4 ft/d)  (20,000 ft2) (4 ft/3 ft)

               = 7.68 ft3/d

               = 57 gal/d.

Decreasing the permeability by a factor of 2 will halve the flow rate.

     Note that this is the flow rate after equilibrium has been reached and
the liner is fully saturated.  A time lapse will occur between the intrusion
of the leachate into the liner and its appearance at the bottom of the
liner.

3.8.2  Hydraulic Gradient

     It is customary to conduct the tests with hydraulic gradients that
are substantially greater than those encountered in the field in order to
measure the permeability of compacted clay within a reasonably short time
period.  The two implied conditions in the Darcy equation are that the flow
rate is directly proportional to the hydraulic gradient and that a plot of
the relationship between flow rate and hydraulic gradient passes through the
origin.  There is no single accepted hydraulic gradient for use in permea-
bility testing.  Thus, gradients of 5 to 20 are recommended by some (Zimmie,
1981) while gradients as high as 362 have been used by others (Anderson and
Brown, 1981).

     Over the past several decades, several studies have been aimed at evalu-
ating the validity of Darcy's law by measuring the dependence of permeability
on hydraulic gradient.  Oakes (1960), Hansbro (1960), Mitchell and Younger
(1967), and others have published data that indicate -a departure from lin-
earity at low hydraulic gradients.  Bowles (1979) observes that in clays a
threshold gradient of 2 to 4 may be necessary to produce any flow.  The
departure from linearity at low hydraulic gradients may not be unexpected
according to Yong and Warkentin (1975).  The binding forces between water
molecules and clay surfaces, in effect, create immobilized hydrodynamic
layers of water surrounding each clay particle.  The thickness of these
immobilized hydrodynamic layers depends upon the extent of interaction
between the water and clay surfaces and upon the driving force for flow.
At sufficiently low hydraulic gradients, the "effective" pore diameter
available for flow could be decreased by the immobilized hydrodynamic
layers.  Several workers, however, have attributed apparent threshold
gradients to experimental artifact.

     The current regulations require that a landfill liner have a leachate
collection system that will ensure that the leachate depth over the liner
                                    3-38

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does  not exceed 30 cm  (1 ft).  Thu;s, for liners exceeding 1 foot in thick-
ness,  the  hydraulic gradient will be less than 2.  In view of the larger
hydraulic  gradients used in laboratory tests, the question of the linearity
of permeability with hydraulic gradient should be resolved, if meaningful
translation of laboratory  results to the field situation is to be expected.

3.8.3   Permeability Measurement Factors That Influence Test Results

      Permeability may  be determined by either a constant head test or a
falling head  test.  In a constant head test, as implied by the name, the
test  sample ,is subjected to the permeant fluid under a constant head (i.e.,
the hydraulic gradient is  constant).  In falling head tests, the head of
permeant fluid is allowed  to decrease (fluid passes through the sample)
during  the timed interval  of the test.

      Equations (3.15)  and  (3.16) are used to calculate permeability through
the methods of constant head and falling head, respectively.


           For constant head,     K = rjr                                (3.15)



           for falling  head,      K = AT ln F                          (3.16)

where

     K  = hydraulic conductivity, cm/s

     L  - length of soil path across which head is impressed, cm

     Q  = volumetric flow rate, cm3/s

     A = cross-sectional area of sample, cm2

     h = hydraulic head, total head

     t = time interval  over which the sample is collected (or readings
         are  taken)

     a = cross-sectional  area of in-flow column

 h ,h  = height of fluid in in-flow column at beginning of test and at
  1  z   the end of test.

     The total head is  actually comprised of three components:   velocity,
elevation,  and pressure head.   Because the seepage velocity in  geotechnical
problems is relatively  low, the velocity head is  insignificant  compared to
elevation and pressure  heads.

     Most permeability  test devices may be operated in the laboratory in
either the  falling head or constant head mode,  depending on the hydraulic
systems connected to the permeameter.  Similarly,  in the field  either a
constant head or a falling head test may be used  to determine flow through
the soil.  Theoretically,  test results (i.e., the  value of K that  is


                                   3-39

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 calculated)  should be the same whether the measurements are made  in a
 constant head-or falling head test.

      Laboratory permeability tests are conducted  to predict performance of
 a natural  or compacted clay liner  in  the  field.   Frequently, however, to
 complete a test within a reasonable time  frame, laboratory conditions are
 established  that differ substantially from conditions  in the field (e.g.,
 elevated hydraulic gradient).  An  understanding of the many factors that
 affect  permeability tests is necessary to extrapolate, in a meaningful way,
 from test results to performance prediction.

      Important  factors that influence permeability measurements include
 sample  characteristics and preparation, permeant  properties, design of the
 test apparatus,  and selection and  controlof variables during test perform-
 ance.   Another  important factor that  has  not been addressed adequately is
 interlaboratory variability in permeability tests.  Regarding variability in
 permeability, Zimmie (1981)  has concluded that, "One is always dealing with
 orders  of  magnitude in permeability problems, and it is unrealistic to expect
 results  to agree within less  than several hundred percent."  Bryant and
 Bodocsi  (1986)  have also examined precisibn and reliability that can be
 achieved in  laboratory measurements.

     A  summary  compiled by Olson and  Daniel (1979) of potential errors in
 laboratory permeability tests is given  in Table 3-4.  The information is
 based on reported permeability test results from  several investigations.
 Another  summary  of sources of error in  estimating field permeability from
 laboratory tests is given  in  Table 3-5.   This table is reproduced from
 Daniel  (1981).                            i

 3.8.3.1  Sample  Selection,  Size, and  Preparation-
     Measuring  the permeability of compacted fill is often accomplished by
 bringing undisturbed samples  into the laboratory.  Samples obtained with
 Shelby  tubes or  similar sampling devices  are considered "undisturbed,"
 although in  reality this is  not the case.  Griffin et al. (1985) and Herzog
 and  Morse  (1984)  found that  hydraulic conductivities measured in the labora-
 tory on  Shelby  tube samples  of a glacial  till were lower than conductivities
 measured in  the  field.  They  concluded  that collection of the Shelby tube
 samples  caused  some compaction and closing of naturaljy-occurring cracks and
 fissures in  the  till.   Boutwell and Donald (1982) measured hydraulic con-
 ductivities  on  large diameter core samples from a compacted clay liner and
 found them similar to  conductivities  measured in  the field.  The specifi-
 cation of  sample selection,  sample size,  sample preparation, and the number
 of samples subjected to testing should  be oriented toward adequately
 representing field conditions.  The number of samples and tests should be
 determined by the level  of statistical  confidence desired combined with the
 precision  and accuracy of  the test method employed.

     Large samples  tested  in  situ (see Section 3.8.5) may be of sufficient
 size to  include  some macropores, holes, natural cracks, or sand lenses.
 Such samples are  more  likely  than much smaller samples to provide good esti-
mates of actual  field  performance.  However, the time required for such tests
may be prohibitive,  particularly if the purpose of the test is construction
 quality  control.   Laboratory  tests are performed on smaller samples but have
 the advantage of a  shorter test time and limited interruption of construction
activities.                               :
                                    3-40

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            TABLE 3-4.  SUMMARY V>OTENTIAL% ERRORS IN LABORATORY
                   PERMEABILITY TESTS ON SATURATED SOIL3
Source of error
     Direction
  of deviation of
measured permeability
 from correct value
Ratio of measured
 permeability to
  correct value
Voids formed in sample
  preparation

Smear zone formed
  during trimming

Use of distilled water
  as a permeant

Air in sample

Growth of microorganisms

Use of excessive hydraulic
  gradient

Use of wrong temperature

Ignoring volume change
  due to stress change

Flowing water in a direction
  other than the one of
  highest permeability

Performing laboratory
  rather than in situ
  tests
        High


        Low


        Low


        Low

        Low

        Low or high


        Varies

        High


        Low



        Usually low
  0.005 to 0.1


   0.1 to 0.5

  0.001 to 0.1

    <1 to 5


   0.5 to 1.5

     1 to 20


     1 to 40



  <0.0001 to 3
aData from Olson and Daniel (1979)
                                    3-41

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          TABLE  3-5.   SUMMARY OF SOURCES OF ERROR IN ESTIMATING FIELD
                  PERMEABILITY OF COMPACTED CLAY LINERS FROM
                              LABORATORY TESTS3
    Potential
 sources  of  error
Laboratory K too
  high or low?
Possible number of
orders of magnitude
     of error
Compaction at a higher
  water  content in
  laboratory than in field

Maximum  size of clay
  chunks smaller in
  laboratory than in field

Deleterious substance (e.g.,
  plant  roots) present in
  the field but not in
  laboratory samples

Use of more compactive effort
  in the laboratory than in
  the field, resulting in
  optimum water content being
  higher in field than in
  laboratory

Air in laboratory samples

Use of excessive hydraulic
  gradient causing particle
  migration

Lack of steady-state seepage
  due to stress change

 Sample size too small  in
  laboratory test

 Desiccation cracks in field
      Low
      Low
      Low
      Low
      Low


      Low



       I
      High

       i
      Low



      Low
      1 to 3
      1 to 2
      1  to 3
      1  to  3
      0  to  1

      0  to  1



      0  to  1


      0  to  3


      No data
Reproduced from Daniel (1981).

bA rough estimate based on available data.
                                   3-42

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      During  the  design  phase  of a  clay  liner construction project, samples of
 clay  soils are obtained from  the site and subjected to a series of laboratory
 tests, which include  the measurement of their permeability in the compacted
 state.   The  manner  in which these  samples are handled and the procedures
 followed during  compaction can greatly  influence the test outcome.  At pres-
 ent,  there are no accepted standard protocols for test sample preparation.

      A recent study of  test methods used by commercial soil laboratories
 (Truesdale et al.,  1985) revealed  that  some used protocols requiring air
 drying the soil  while others  required that it be maintained at or near the
 field moisture content  before clod size reduction.  Reasons given for drying
 were  that it made it  easy to  break up clods, sieve the soil, and obtain a
 very  homogeneous soil mass for testing.  The problem with drying, however,
 is that  there is no way of knowing if the dried soil can be rehydrated to
 its former condition.   Sangrey et al. (1976) found that drying and rewetting
 significantly altered the liquid limits of several clays.  Typically, re-
 hydration took several  weeks  rather than the 24 hours commonly allowed for
 most  laboratory  tests.   More  important was their finding that some clays were
 irreversibly altered  by drying.

      Truesdale et al. also found a variety of methods for reducing clod size
 and obtaining a  uniform representative sample for compaction.  When dry soil
 was used, the clod  size  reduction methods included grinding the clods in an
 electric  mill, breaking  the clods up with a hammer, and manually crushing
 them  between a hand-held steel plate and a counter top.  Typically, the
 ground sample is passed  through a No. 4 sieve before being rewet and
 compacted.

     Wet  samples were also handled in a variety of ways.  These included
manually  breaking the clods, forcing the moist clay through a ,No. 4 sieve,
 and mixing and grinding  the soil  in a Hobart®vegetable shredder.

     Several  techniques have been developed for compacting clay soil
 samples.   In general, the soil is compacted in a cylindrical  compaction
mold.  If a  fixed-wall permeation test is to be run, the clay can be
 compacted directly  in the permeameter, which in this instance serves as
 the compaction mold.  Alternatively,  clay can be compacted in a separate
 compaction mold,  extruded,  and then trimmed to fit th,e permeameter.  At
 some facilities,  a split mold is  used.

     A variety of methods are available for compacting test samples in the
 laboratory.   Among these are:

     t  Static Compaction—A hydraulic or mechanical  press is used to
        compress  a predetermined  weight of soil  into a mold of known
        volume (to the required density).

     •  Impact Compaction—A drop hammer is  used to compact the specimen.
       Often the compaction is done  according to the ASTM procedure for
       determining  the moisture  density curve.   The procedure is often
       modified  to  accommodate various-sized compaction  molds.
                                    3-43

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      •  Kneading Compaction—This may be accomplished with a device known as
         a Harvard Miniature Compactor.  Some  investigators think this device
         mimics the kneading compaction obtained  in  the  field with sheepsfoot
         rollers.

      0  Manual Compaction—In some laboratories,  soil samples are weighed and
         pushed into a mold of known volume with  a handheld ram or rod.

      Recently, Dunn and Mitchell  (1984)  reported  on a series of permeability
 tests in which the only difference was the method of compacting the sample;;.
 When samples were compacted by different methods  to both 90 and 95 percent of
 their maximum dry density, differences in their  hydraulic conductivities were
 notable.  At both dry densities,  the static compaction  produced samples with
 higher hydraulic conductivities than kneading, which was second highest, or
 impact,  which was lowest.   Manual  compaction methods were not tested.

      The results of Dunn and Mitchell's  (1984) study indicated that static
 compaction produced replicate samples with the least effort.  The higher
 hydraulic conductivity obtained with this method  correlates better with
 field-compacted samples than the  other commonly used compaction methods.

      Regardless of the compaction  method used in  the laboratory, the final
 sample should not be considered equivalent to the same material compacted
 in  the field, for several  reasons.   Field compaction is done with machines
 whose size and compactive  effort are not duplicated in the laboratory.
 Clod sizes,  which are very small and fairly well  controlled in the labora-
 tory,  are much more variable in the  field, where  clod size may range up to
 6 or 8 inches or even greater in some  cases.  Finally, moisture content and
 distribution in laboratory samples are controlled much more carefully than
 in  the field,  where the combination  of large clods and inadequate curing
 (soaking)  time after water addition  may  result in nonuniform moisture dis-
 tribution within a liner.   The  profound  effect of moisture content on
 permeability is  discussed  in Chapter 2 (Section 2.4.2).

      The'significance of sample diameter  has been investigated by Daniel
 (1981).   His  data show that  permeability determined on the specimens tested
 in  the laboratory drastically underestimated the actual  permeability of a
 clay  liner.   Test results  on different diameter samples of a compacted clay
 liner  are  shown  in  Table 3-6.   The average permeability of the in-place
 liner was  back-calculated  from measured  leakage rates and found to be
 1 x  10~5  cm/s.   Boynton  and  Daniel (1985) compacted test samples with
 various diameters  ranging  between  1.5 and 6 inches.  The measured hydraulic
 conductivities  showed  an increase with sample diameter,  with the smallest
 diameter  having  the  lowest  conductivities.  However, the highest and lowest
 conductivities differed  only by a factor of 2, which the authors did not
 consider to be of practical  significance.

     Anderson and Bouma  (1973) experimented with a series of cores of
different  lengths to determine the effect of sample size on  permeability.
They found that permeabilities for cores ,17 cm in length were lower by
one-half an order of magnitude than for the 5-cm-length  samples.
                                    3-44

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   TABLE 3-6.  TEST RESULTS SHOWING EFFECT OF SAMPLE
        DIAMETER ON PERMEABILITY MEASUREMENTSa
Sample diameter (cm)                 Permeability (cm/s)

        3.8                                1 x ID"7
        6.4                                8 x ID-9
      243.8                                3 x ID'5
aData from Daniel  (1981).
                         3-45

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      Whether a sample is compacted dry of optimum  or wet  of  optimum can
 profoundly influence the resulting permeability.   Daniel  (1981)  reported
 that the permeabilities of soils  compacted dry  of  optimum might  typically
 be 10 to 1,000 times greater than permeabilities of the same soils compacted
 wet of optimum (this phenomenon  is discussed  in Section 2.3).  Because mois-
 ture conditions at compaction can strongly influence permeability measure-
 ments, gross errors in predicting field permeability from laboratory tests
 may occur if compaction is performed  at different  water contents.  Permea-
 bility tests can be conducted with samples compacted at several  points in a
 range of moisture contents to ensure  that actual field moisture  conditions
 are reproduced.

      Another consideration is that equipment  used  to compact laboratory
 samples does not resemble  field compaction equipment.  Lambe and Whitman
 (1979), in  comparing field and laboratory compaction efforts, have concluded
 that generally the laboratory curves  yield a  somewhat lower  optimum water
 content than the actual  field optimum.

      In the field,  a compacted low-permeability soil may  display anisotropic
 flow characteristics.   The horizontal  permeability (parallel to  the plane
 of compaction)  of anisotropic soil  may be much  higher than the vertical
 permeability (normal  to the plane of  compaction).  Such a condition will
 lead to predominantly  horizontal  flow.   For in-place stratified  clays, the
 ratio of horizontal  to vertical permeabilities  may exceed 10  (Olson and
 Daniel,  1979).

      In contrast,  however,  Boynton  and  Daniel (1985) report  that no anise-
 tropic flow was found  in laboratory-prepared  samples of fireclay compacted
 wet of optimum.  Anisotropic flow found  in  compacted soils may be the result
 of poor lift bonding or variations  in  density within the  test sample.

 3.8.3.2  Hydraulic  Gradient--
      Si nee  Darcy's  law indicates  a  linear relationship between flow rate and
 hydraulic gradient,  many workers  have  used  elevated hydraulic gradients to
 reduce testing  time.   However, if hydraulic gradients are excessive, piping
 (opening  flow channels and  increasing  hydraulic conductivity) or particle
 migration  (blocking  flow channels and  reducing  hydraulic  conductivity) may
 occur and can  significantly influence  permeability measurement.  Although
 such  effects  can  occur and  have been  reported (Daniel, 1981; Mitchell  and
 Younger,  1967),  studies have  been  conducted at  elevated gradients with no
 evidence of  piping  or  particle migration  (Anderson, 1981).

      Excessive  hydraulic gradients  can  result in deviations from Darcy's law,
which  is only valid  for laminar flow conditions.   Even under gradients as
 high  as 361,  however,  velocities  low enough to assure a Reynolds number
within  the  laminar  flow regime are  assured due  to  the very small  particle
diameters 1n fine-grained  soils.

      Zimmie et  al.  (1981) have recommended use of hydraulic gradients
between 5 and 20 for laboratory studies.  Research performed at Louisiana
State University has lead to  the conclusion that tests conducted under
hydraulic gradients as high as 100 are "acceptable for testing,  reducing  ,
testing times to realistic and practical duration"  (Acar and Field,  1982).
                                    3-46

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Dunn and Mitchell  (1984) reported that increasing the gradient in steps from
20 to 200 caused an  irreversible decrease in hydraulic conductivity.  They
attributed mast of the observed,,changes to particle migration due to seepage
forces.  They recommend that test gradients be kept as low as possible while
still allowing the test to be completed in a reasonable time.

3.8.3.3  Sample Saturation--
     A soil sample,  even when compacted, has some porosity.  The pores are
filled with either gas (generally air) or liquid.  Because liquid water
cannot flow through  a gas bubble, entrapped air within the interconnected
pores that form flow channels for the permeant fluid causes a reduction in
flow and a corresponding apparent decrease in permeability.  Soaking the
sample from the bottom with the top open to the atmosphere may not result in
complete saturation.  Smith and Browning (1942) found that in 200 specimens
soaked from the bottom, the degree of saturation averaged 91 percent, with
the lowest value at  78 percent.

     The extent of the error in permeability measurement attributable to
entrapped gas bubbles is not fully known, although decreases in permeability
by factors ranging from 2 to 5 have been reported (Johnson, 1954).

     The use of backpressure in permeability testing is considered by some
researchers to be necessary for saturating a soil sample.  Matyas (1967),
investigating the effect of saturation on permeability, applied a back-
pressure of 5 psi to "saturate a clay specimen."  According to his calcula-
tions, this pressure was not sufficient to guarantee complete saturation.
After the saturation attempt at the low pressure, the specimen was subjected
to different hydraulic gradients, and discharge velocities were measured.
Similar samples were saturated at 24 psi  and at 70 psi.  The plot of
hydraulic gradient versus discharge velocity is shown in Figure 3-16.

     Matyas1  data indicate that at 5 psi  backpressure the velocity gradient
plot does not pass through the origin and is nonlinear.  However, when the
backpressure was raised to either 24 psi  or 70 psi,  the velocity gradient
relationship was found to be linear and to pass through the origin.  The
apparent nonlinear velocity gradient relationship was attributed to the
presence of air in the voids.  There was no evidence of a threshold gradient
(i.e., a gradient below which flow would not occur).
                                                     *
     Matyas (1967) did not address the difference in the velocity gradient
relationships at backpressures of 24 and 70 psi.  One might conclude that
the application of higher backpressures caused some  particle rearrangement
resulting in lower observed permeability values.  The lowest practical
backpressure to obtain saturation appears desirable  in order to minimize
these effects.  The effects can also be minimized if the backpressures are
increased incrementally and sufficient time is allowed between successive
increases so that high seepage forces do not develop in unsaturated portions
of the specimen.  Daniel  et al. (1984) reports using backpressures of 40 to
60 psi applied in 10-psi  increments.  Each increment is held for a period
ranging from several  minutes to several  hours.  Full backpressure is main-
tained for 1  to 5 days before the test is begun.
                                    3-47

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   3 X  10
   2 X 10~5
u
o
o
>  1 x 1(T5
                           246

                                 Hydraulic Gradient
  After Matyas, 1967


   Figure 3-16. Effect of backpressure on permeability to water, Sasumua clay.
                         3-48

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 3.8.3.4  Permeant Characteristics--
      Permeant fluids that are commonly used to determine baseline permea-
 bility values-include deionized water, tap water, groundwater (representative
 of a specific site) and standard permeant solution, typically 0.01 N calcium
 sulfate or calcium chloride.  The standard solution is intended to simulate
 the hard water frequently used in the field during installation and subse-
 quent hydration of a.clay barrier.

      While some researchers claim that use of different fluids can influence
 baseline permeabilities, others do not believe the effects  are significant
 (Olson and Daniel, 1981).  Recently,  the trend has been toward using the
 standard calcium solutions for initial saturation and  baseline permeability
 determinations.

      In quality control  and in compatibility testing,  factors that influence
 the flow characteristics of a permeant fluid will  alter the apparent soil
 permeability to that fluid.  Because  viscosity and density  are temperature-
 dependent properties of  a fluid,  seasonal  temperature  changes in  the field
 could influence the range of permeabilities  to be  anticipated.  Large
 variations  in temperature over a  test sample are  unlikely,  however.  Soil
 permeabilities are sometimes expressed as  intrinsic permeabilities  (see
 Equation  3.15 in  Section 3.8.1) to account for differences  in flow  properties
 between different permeant fluids,  or at different temperatures.   However,
 the use of  the permeability coefficient, K,  is  much more common and  is used
 throughout  the remainder of this  section.

      The  presence of certain chemicals  in permeant fluids has  been  shown to
 alter the permeability of clay soils  (see Chapter  4).   Shrinkage  of  clay
 particles may result from changes  in  interlayer spacing due  to  interaction
 of  chemicals  with the clay particle's  double  layer.  Changes  in adsorbed
 cations or  the presence  of salts  or acids in  the permeant fluid can  also
 effect  significant  permeability increases.   Such effects are  the  reason for
 conducting  compatibility tests.   Effects of  chemical permeants may be evident
 immediately after the permeant penetrates the  sample, or the  effect may not
 be  seen until  one or more  pore volumes  have  passed  through the  sample.  These
 effects are discussed fully  in Chapter  4.

 3.8.3.5  Test  Duration—
     A  number  of  factors  can  cause changes in permeabjlity with time.  It
 is  essential  in permeability  testing  that flow  through  the sample be con-
 tinued  until  stable  permeability measurements are  obtained.   In compatibility
 testing, several  pore volumes  of  fluid  should be passed through the  sample
 to  ensure that any  tendency  toward an  increased or decreased permeability is
 observed.   The ultimate  permeability  cannot be  established if the permea-
 bility  changes appreciably with time.

     Under  conditions of constant applied stress,  changes in pore pressure
 can cause changes in sample volume.   In a constant head test, some of the
 initial measured  in-flow into  the sample compensates for the volume change
 rather than being the result of steady-state seepage (Olson and Daniel,
 1979).  Permeability tests should be run long enough to ensure that steady-
state values are obtained.  Peirce and Witter (1986) discuss several methods
for developing termination criteria in tests with water and other chemical
solutions.             -.'"-"
                                    3-49

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     Some clays exhibit thixotropic behavior; their internal structure
and flow characteristics change with time.  These changes can increase
permeability with time because of larger effective pore sizes in the clay.
Mitchell et al. (1965) found measured permeabilities to be as much as six
times greater  for samples tested at 21 days compared to samples tested
immediately after compaction.  Dunn and Mitchell (1984) reported similar
results.  Boynton and Daniel (1985) did not observe thixotropic changes
in stored samples; but they attributed this to their having compacted them
dry of optimum, whereas Mitchell et al. (1965) and Dunn and Mitchell (1984)
compacted wet  of optimum.

     Although  not usually a significant factor, microorganisms present in
test samples have been shown to influence permeability by clogging the flow
channels with  organic matter or with gases produced by the microorganisms.
Allison (1947) reported long-term permeabilities of sterile soils to be 8 to
50 times lower than the values of nonsterile soils.

3.8.4  Laboratory Permeability Tests

     Examples  of permeability test devices and the methods used for testing
are described  briefly below.  The emphasis of the discussion is on features
that distinguish the various devices and their advantages and disadvantages.
The relative merits of fixed- and flexible-wall permeameters are discussed by
Daniel et al., 1985.

3.8.4.1  Pressure Cell--
     The accepted standard test for laboratory determination of saturated
permeability in the agricultural sciences (but not the geotechnical sciences)
1s called the  pressure cell test.  In this procedure a soil sample, which may
be an undisturbed core, a sample compacted in a mold, or a volume of soil, is
placed in a metal pressure cell.  After the soil is initially saturated, it
1s connected to a standpipe.  The permeant fluid is introduced through the
standpipe and  forced through the pressure cell under a falling head.  The
standpipe may  or may not be connected to a source of air pressure to super-
Impose a pressure head over the fluid column.  The pressure cell apparatus
for a falling  head test is illustrated in Figure 3-17.  A constant head test
could also be  conducted in the pressure cell  by measuring the volume of the
effluent forced through the sample within a timed interval.

     Saturation of the sample core is usually accomplished by submerging one
end of the core 1n a pan of water for 16 hours with the other end open to the
air.  This procedure may not be adequate to saturate the sample completely
prior to the permeability test.  Vacuum wetting and fluctuating external gas
pressure are alternate saturation techniques that may be used with the pres-
sure cell.

3.8.4.2  Compaction Permeameter—        ;
     The compaction permeameter (also called a fixed-wall permeameter) has
been developed for testing permeant fluids with a compacted soil layer.  One
advantage over the pressure cell is that the sample is compacted directly in
the permeability test device.  As a result, a better seal is obtained between
the sample and the walls of the test vessel.  To ensure a good sidewall seal,
some workers apply a bentonite slurry to the Inside of the chamber before the
sample is introduced.  Silicon grease has*also been tried.  As with the pres-
sure cell, the compaction mold may be used in either a falling head test or
a constant head test.  The compaction permeameter may be modified so that

                                    3-50

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         To drain
         Porous plate
                                                           	Standpipe
"O" ring seals
        Porous plate
                                 Overflow (Fixed level)

                       To water source •
                     for filling standplpe
                                              2-way stopcock
After Klute, 1965
              Figure 3-17. Apparatus for pressure cell method.
                                3-51

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 elevated pressures  can be superimposed to reduce the testing time.  A
 modified compaction permeameter is illustrated in Figure 3-18.  Not shown
 on the diagram  is the source of compressed air with a water trap, regulator,
 and pressure meter. Also not shown is a fraction collector with automatic
 timer that handles  the collection and isolation of effluent samples.

     The sample is  leveled and the fluid^chamber is slowly filled so as not
 to disturb the  sample surface.  The filled permeameter is allowed to stand
 for a period of time (typically overnight or longer) to allow hydration and
 swelling of the clay.  Pressure is applied to the sample only after it has
 completely hydrated.

     In compatibility testing, baseline permeability determinations are
 often obtained  with the standard permeant fluid before the test permeant is
 introduced.  Alternatively, baseline values are obtained in separate tests
 with other samples  of the same soil.

     A recent modification of the compaction permeameter device is the
 double-ring permeameter.  This apparatus has been developed for use in
 compatibility tests involving waste leachates that may cause sample volume
 changes during  testing (Anderson, 1983).  In the double-ring permeameter
 test, a soil sample is compacted in a cylindrical mold that is mounted on
 a base plate with a short cylindrical section mounted on its upper surface
 (Figure 3-19).   Separate outlets in the inner and outer rings serve to
 separate sidewall leakage from flow through the central soil matrix.  This
 type of device  may  be especially useful for tests with soils that are liable
 to undergo volume changes during permeability testing.  Also, the double-ring
 permeameter is  appropriate for use in compatibility tests that involve
 liquids that may cause shrinkage of the sample due to development of soil
 structure.                               ;

     Testing in  the double-ring permeameter begins by passing sufficient
 standard permeant fluid through the soil to obtain stable baseline perme-
 abilities for both  the inner and outer compartments.  If the permeability
 of the outer compartment is significantly higher than that of the inner
 compartment, the soil core is discarded and a new core is compacted in the
mold.  After stable baseline permeabilities are obtained, the standard
permeant is replaced by the test fluid, which is then passed through the
 sample.  The volume passed through each compartment to measured and reported
based on the pore volume of that compartment.

     Tests in the double-ring permeameter are usually conducted with a con-
stant elevated hydraulic gradient.  They also can be performed as a constant
head test without superimposed air pressure.  As in other tests,  100-percent
saturation of the sample may not be achieved unless backpressure is used.

     Permeability value,  leachate volume, and time increment are recorded
for discrete volumes of permeant fluid passed through both chambers during
a compatibility test.  Permeability measurements are then plotted versus
the total  number of pore volumes passed through the sample.  Data plotted
in this way indicate changes in permeability that might be expected for a
clay liner in service over a period of time that corresponds to the number
of pore volumes exchanged in the test.
                                    3-52

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         Pressure intake
Sealing gaskets
                                           Pressure release
                                                    Top plate
Clamping stud
                      Outlet
                                                   Base plate
                                            Porous stone insert
            Source: Anderson and Brown, 1981




             Figure 3-18. Modified compaction permeameter.
                              3-53

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01
                                  Permeameter
                                  Base Plate
                                              Outlet for
                                              Inner Ring
Outlet for
Outer Ring
                                                                                                                          Outer Ring
                  Source:  Anderson, 1983
                                       Figure 3-19. Detail of the base plate for a double-ring permeameter.

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      Because the double-ring device has been introduced only recently,
 a criterion has not been established to determine what constitutes a
 significant difference between the permeability in the central  compart-
 ment and that in the annular space.  This criterion needs to be developed
 if the device is to be widely used.

 3.8.4.3  Triaxial Cells--
      Samples prepared for triaxial testing consist of cylindrical  columns
 of compacted soil encased laterally with a flexible membrane (often latex
 rubber) and enclosed at the ends with porous stones.  The enclosed soil
 sample is placed in a water-filled cell that can be pressurized to provide
 a confining pressure on the sides of the sample (Figure 3-20).   The sample
 to be tested may be prepared in a compaction mold and extruded  for testing
 in the triaxial  cell.  Samples are typically 2 to 4 inches in diameter.
 Undisturbed Shelby tube samples may also be tested.

      Permeability tests are usually performed by passing permeant  liquids
 upwards into the sample under pressure while maintaining a lower pressure
 at the exit port on the top of the sample.  A confining pressure somewhat
 greater than the pressure under which the liquids enter the soil is imposed
 to press the flexible membrane firmly against the soil  sample,  preventing
 flow along  the sidewall.   The confining pressure on the soil  sample should
 be selected to simulate the lateral  pressures a material  will experience  in
 the  clay liner.

      Sample saturation is accomplished by forcing  a standard  permeant  liquid
 upward through the  sample.   Backpressure may be applied to hasten  the  dis-
 solution of trapped air bubbles  or gases generated by  reactions  between
 permeant liquid  and the sample.   The  use of  backpressure  ensures virtually
 complete saturation of the  sample,  a  factor  that probably contributes  to  the
 good  reproducibility of triaxial  tests.   Pressure  regulators  and electronic
 pressure transducers are  used to  control  and monitor sample stress  conditions
 and  to  assess the saturation  state within  the sample during testing.

      In a typical test,  sufficient  standard  liquid is passed  through the
 sample  to establish a  stable  baseline  permeability before  the test  permeant
 fluid  is  introduced.   For some tests  the test permeant  is  introduced directly
 with baseline being determined with another  soil  sample.   The test may be
 conducted as a constant head  or falling  head test.  Permeability value,
 leachate volume, and  time  increment are  reported for each  volume of test
 fluid passed through  the  sample.  These  data are used to plot permeability
 versus  pore volumes  of  test fluid passed.

     Excellent precision  (+20 percent) based  on  four samples has been
 reported for the apparatus~s.hown  1n Figure 3-20  (Haji-Djafari and Wright,
 1982)•

     Questions have been  raised about whether triaxial cells are appropriate
 for compatibility testing of permeant fluids  that may cause the  soil sample
 to shrink (Chapter 4).  Because of the confining cell pressure,  the flexible
membrane will contract with the soil sample so that shrinkage cracks that
 could occur 1n a field situation and that might appear 1n fixed-wall devices
as sidewall  leaks would not be simulated in the triaxial cell.  Not all
 researchers  agree on this issue since the effect has not been demonstrated
                                    3-55

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                                          CELL
                                        PRESSURE
                                         SOURCE
                                     (COMPRESSED AIR)

                                           
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clearly in comparative tests.  Boynton and Daniel (1984) have shown that
cracks in des-iccated and rewet samples would only partially close unless
substantial effective stress were applied.

     Although conventional triaxial cells are not designed to withstand
concentrated chemical permeants, several modifications are possible to
minimize the problem of chemical attack on the test device.  Polyethylene,
nylon, or Teflon® fittings may be used in place of the customary brass or
steel fittings.  The use of colostomy bags (of the type used in surgical
applications) in place of the conventional latex membrane has also been
reported for use with wastes such as gasoline (J. Withiam, D'Appolonia
Consulting Engineers, Inc., Pittsburgh, PA, personal communication, 1983).
Samples may also be wrapped in thin Teflon® tape to prevent contact between
the permeant and the latex membrane.

3.8.4.4  Consolidation Cells--
     Consolidation cells (consolidometers) are commonly used in the field of
geotechnical engineering to determine the compressibility and rate of settle-
ment of soils.  Consolidation occurs when water is squeezed out of the soil
and is therefore a function of permeability.  A fixed-ring consolidation cell
can be used to measure permeability (Figure 3-21).

     The consolidation cell method is routinely used in testing permeability
for applications such as earth dams, retaining walls, and slurry trenches.
The method has not been widely used in the evaluation of chemical compat-
ibility with clay liner material.

3.8.5  Field Permeability Tests

     The permeability of clay liners can be determined in the field by per-
forming bore hole permeability tests or by using porous probes, air entry
permeameters, the Guelph permeameter, or ring infiltrometers.  The reader
is advised to consult EPA method 9100 "Saturated Hydraulic Conductivity,
Saturated Leachate Conductivity, and Intrinsic Permeability" (U.S. EPA,
1986), which contains the EPA recommended procedures for the Subtitle C
(Hazardous Waste) RCRA program.

3.8.5.1  Bore Hole Tests—
     The two stage bore hole permeability test was developed by G. Boutwell
and described in Boutwell and Derick, 1986.  The discussion provided here is
based on Daniel, 1987.

     To perform this test, a hole is drilled into the clay liner and a casing
is installed and grouted around the outside.  The depth of the hole must be
at least 5 times greater than its diameter and the distance between the
bottom of the hole and the liner bottom must be greater than 5 diameters.

     After placement, the casing is capped and both casing and stand pipe are
filled with water (Figure 3-22).  The Stage I test consists of a series of
falling head tests in which the head (H) driving the flow is measured from
                                    3-57

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                     Vertical Stress

                            T      Pressure
           Permeant Ruid
           ,n,e«
Effluent
Outlet-
               LT
                                   Outlet
                                        irn
                          Soil
u
                                              Porous Stone
            Figure 3-21. Consolidation permeameter.
                            3-58

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      H
             STAGE I

             .2.
    Clay Liner
'Casing
• Grout
                         >5D
                         >5D
H
                            STAGE II
                             .2.
                    Clay Liner    D
                                          >5D
                                                                 >5D
Figure 3-22. Two-stage, borehole permeability test (Boutwell and Oerick, 1986).
                                 3-59

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 the bottom of the bore hole.  The Stage I hydraulic conductivities (ki)
 are computed as follows:
                                 (t  -
                                             in OyH-)                  (3.17)
      The steady state value of ki is found by plotting  the  computed  ki  values
 as  functions of time.  For the second stage of the  test the top  of the  per-
 meameter is  removed and the hole is  made deeper.  The new uncased segment  of
 the hole must have a length to diameter ratio (L/D)  of  between 1 and 1.5.  A
 second  series of falling head  tests  Is performed  in  which the head (H)  is  is
 measured from the midpoint of  the new uncased section of the bore hole.  The
 Stage II hydraulic conductivities (k2)  are computed  as  follows;


                             k2 = (A/B)  in  (Hj/Hg)                       (3.18)

 where                                   .


      A  - d2  (in  [(L/D)  + (1  +  (L/D)2)172])                              (3.19)


      B  = 8D  (L/D)  (1- 0.562  exp  [-1.57  (L/D)])                          (3.20).

      The steady  state value  of k2 is  found  by plotting  the  k2 values as
 functions of time.

      A  parameter m  is defined  as:
where

     kfo = horizontal hydraulic conductivity

     kv = vertical hydraulic conductivity           "

     Arbitrary values of m typically ranging from 1 to 10, are chosen and
used to compute values of k£/ki by substituting into the following
expression:


                                                   211/2.I
                            In J(mL/D) + [1 + (mL/D)2]1/2£
                                   3-60

-------
     Next, the chosen values of m and the corresponding computed values of
k2/ki, are plotted.  The real value of k£/ki is then determined using the
k2 and kj valties obtained from equations 3.18 and 3.17.  The k2/kj vs.
m graph is then used to find the m value corresponding to the real
value.  Finally, the horizontal (k^) and vertical (kv) hydraulic
conductivities are calculated from the following equations:
                                kh = mki                               (3.21)

                                kv = (l/m)ki                           (3.22)
     According to Daniel (1987), "The advantages of borehole tests are that
the devices are relatively easy to install, they can be installed at great
depth, the cost is relatively low, the hydraulic conductivity in both the
vertical and horizontal directions can be measured, and relatively low
hydraulic conductivities (as low as about 1 x 10~9 cm/s) can be measured.
The disadvantages are that the effects of incomplete and variable saturation
are unknown, the influence of soil suction upon the results is ill defined,
the test cannot be used near the top or bottom of a liner, and the volume of
soil that is permeated is relatively small.  Boutwell and Derick indicate
that the test has worked well and present several case histories."

3.8.5.2  Porous Probes—
     The porous probes are small cylindrical devices, with a porous section
near the tip, that can be pushed or driven into the soil.  Following emplace-
ment, the tip is filled with water and measurements of the rate at which the
water passes out into the surrounding soil are used to compute the horizontal
permeability.  A porous probe is illustrated in Figure 3-23.  In one com-
mercially available unit, air pressure is used to supply the driving head
(Torstensson, 1984).  When using a porous probe, several important
assumptions have to be made  (Daniel, 1987).  These are:

     t  The pore water pressure in the soil surrounding the probe is known

     t  The degree of saturation does not vary in the soil volume through
        which the permeant flows

     «  The soil has not been unduly disturbed by the insertion of the probe.
                                                     «
     Porous probes are easy to install and, in the case of one commercially
available unit, produce results within several hours.  Among their dis-
advantages is their small size which only allows the permeation of small
volumes of soil .

     In field tests, porous probes yielded permeability values that were in
good agreement with both laboratory and sealed double ring infiltrometer
tests.  (Chen and Yomamoto, 1987;  Petsonk et al., 1987).
                                    3-61

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             Refill
            Seal
                                 Flush
                              Porous
                          s^ Material
                       V
Figure 3-23. Installed porous probe (DanieJ, 1987).
                      3-62

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 3.8.5.3  Air-Entry  Permeameter--
     An air-efitry permeameter  is used to measure soil air-entry values from
 which  permeabilities can be calculated.  In a saturated soil in which the
 pressure head  is decreasing, the negative pressure head at which air first
 enters the  soil and becomes essentially continuous in the soil pores is
 called the  air-entry, value.  Conversely, when an unsaturated soil is wetted,,
 the pressure head of water in  the soil increases and that point at which
 water  has displaced most of the air and has become essentially continuous in
 the pores is called the water-entry value (or air-exit value).  In a number
 of granular materials the water-entry value is about half the air-entry value
 (Bouwer, 1978).

     An air-entry permeameter  consists of a metal cylinder, approximately
 25 cm  in diameter,  fitted with an air tight top equipped with a water supply
 reservoir,  a vacuum gauge, an  air escape valve, and as depicted in Figure
 3-24, a tensiometer.  The cylinder is embedded in the soil test patch to a
 depth of approximately 10 cm and the unit is filled with water, all air being
 allowed to  escape through the  air escape valve.  This valve is closed and
 water  is periodically added to the reservoir as infiltration of the soil
 takes place.   When  the wetting front has reached a depth of 10 cm, no more
 water  is added to the reservoir and the supply valve is closed.  The wetting
 front depth is estimated on the basis of past experience with the unit or, if
 a modified  unit is  being used, on the basis of the tensiometer readings.
 After closing  the supply valve, the wetting front no longer advances and the
 pressure gauge will start to display negative pressures that reach a minimum
 value when  the air-entry value of the wetted zone is reached.  (The negative
 pressure develops as a result  of water being sucked into the unsaturated soil
 below the wetting front).  At  this point, air will start to bubble up through
 the wetted  zone increasing the pressure of the aboveground water in the
 device.  Once  the minimum pressure is achieved, the test is terminated, the
 device is removed,  and the actual depth of the wetted front is determined by
 digging a hole and  observing the extent of infiltration (This may be
 difficult in clay that has been compacted wet of optimum.)  This last step is
 not required if a tensiometer has been used.  The air-entry value (Pa) is
 calculated  by  the equation:
where
        Pa = air-entry value of soil expressed as pressure head at point of
             air entry, cm water

      pmin s minimum pressure head as measured with the pressure gauge,
              cm water

         G = height of gauge above soil  surface, cm

         L = depth of wetting front (depth of tensiometer),  cm
                                    3-63

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               H
Soil surface
                                   r
Reservoir

Vacuum guage

Supply valve
Tensfometer
                                                    Air escape valve
                                                          C-cIamp
                                                          Gasket

                                                     Cylinder wall
                                               Wetting  front
         After US. EPA, 1984
                Figure 3-24. Modified airrentry permeameter.
                                3-64

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      The  saturated  hydraulic  conductivity  is calculated by the following
 equation:    -                    V         ":•••


                           K    2  (dH/dt)  L  (Rr/Rc)2
                            "   Ht +  L + l/2(Pa)

 where

      dH/dt  =  rate of  fall  of  water level in reservoir just before the supply
              valve  is  closed,  cm/s

        Ht  =-height above  soil surface of  reservoir water level at time the
              supply valve  is  closed,  cm

        Rr  =  radius of reservoir, cm

        Re  =  radius of cylinder,  cm.

      Daniel (1987) states  that several important assumptions underlying the
 use of air  entry permeameters are:

      •  The suction at base of the wetting front is the water-entry value

      •  The water-entry value is  one-half  the air entry value

      •  The water pressure read on the pressure gauge during the second stage
        of  testing is  (when corrected for  elevation) the negative of the
        air-entry suction

      •  The air-entry  permeameter is completely rigid

      •  The soil is incompressible

      •  The air in the soil beneath the wetting front is at atmospheric
        pressure.

      Daniel asserts that these assumptions are unprotfen and in some cases
unlikely to be correct.

      The advantages of the air-entry permeameter are that relatively rapid
measurements can be made, a relatively large surface area is tested and the
permeability is measured vertically within the confines of the embedded
ring.  The disadvantages are that the depth of soil  tested is shallow, and
very  low infiltration  rates are difficult to measure because of thermal
effects and compliance of the permeameter  itself (Daniel,  1987).

     Topp and Bins (1976) found that the air-entry permeameter gave repro-
ducible values of permeability at various depths in  a number of different
soils.  They also found that results were consistent with  values  obtained
from determinations made on laboratory cores.   Although the laboratory core
                                    3-65

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 permeability was generally  lower than the permeability determined by the
 air-entry permeameter, this was probably due to lack of worm holes or cracks
 in  the  laboratory  samples.  Aldabagh and Beer (1971) found the method to be
 consistent and  reasonable with variability substantially less than the
 natural variation  of  soil.

     Knight and Haile (1984) used an air-entry permeameter on an earthen liner
 and measured permeabilities between 5 x 10~9 an 3 x 10~7 cm/s.  Undis-
 turbed  samples  subjected to laboratory tests had permeabilities about one-
 half order of magnitude less than measured with the air-entry device.

 3.8.5.4 The Guelph Permeameter--
     The Guelph permeameter (manufactured by Soilmoisture Equipment Corp.,
 Santa Barbara,  California) derives its name from the University of Guelph, in
 Canada, where it was  developed.  The device consists of a simple Mariotte
 bottle  device that, when installed in a bore hole, can be used to measure the
 "field  saturated"  hydraulic conductivity of the surrounding soil.  A sche-
 matic diagram of the  device is shown in Figure 3-25.

     The use of this  device is based on the theory that, when a bore-hole 1n
 soil is filled  with water to a constant height, a bulb shaped zone of satura-
 tion is established around the hole.  (See Figure 3-25).  Once the saturated
 zone is established,  the outflow of water becomes constant.  The rate of out-
 flow associated with  each of two different water depths along with the radius
 of  the  bore-hole can  be used to calculate the field saturated conductivity of •
 the soil .

     The following generalized equation solves for field saturated con-
 ductivity (permeability) using data generated by the Guelph permeameter
 (product literature):
where
                  =
                2   TT [ 2 Hj H2 (H2 - Hj);* a2
                                       [H
                               G  s G  —
                                           c]
                               Q2 - (X)  (R2)

                               Q  - (x)  (R)
                                    3-66

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                                      Air Tube
         Water Supply
  Seal
       Partial Vacuum, PI


*	Water Column, P£
         Atmospheric Pressure, PQ

                Soil
                                                          Zone of Saturation
Figure 3-25.  Schematic diagram of Guelph permeameter (P<\ + P£ = PQ)-
                              3-67

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 and                                      ;

           a  ="wen  radius,  cm

      C..,  C2  =  proportionality  factors dependent primarily on  ^1 and ^2
               respectively               ,                     a      a


      HI,  \\2  =  well  height for  first and second measurements respectively, cm

           K  =  permeability,  cm/sec.

      R!»  RE  =  steady-state  rate  of fall of water, in the reservoir of the
               permeameter,  corresponding to HI and H2, respectively, cm/sec.

           X  =  reservoir  constant corresponding to the cross-sectional area,
               cm^

      The  advantages  of the  Guelph permeameter in measuring the permeabili-
 ties  of soils  in situ include  the following (product literature):

      t  Instrument  is portable,  lightweight, easily assembled in the field,
        and  easy to  use.

      •  Assembly and measurements require only one person, and only 2.5
        liters of water  is  needed to operate instrument.

      •  Design is simple so  that serviceability is easy.

      •  Measurements are easily  defendable because the method is based on the
        fundamental, firmly  established constant head well principle.

      In spite  of these advantages, there are some significant disadvantages
 in using  the Guelph  permeameter  to measure clay liner permeabilities.  One
 disadvantage is that it takes  a  long time to obtain results in fine grained
 materials.  Measurements in  coarse grained soils can be completed within a
 couple of  hours at most, but compacted clays can require 2 to 3 days
 (Bradshaw, 1986).  This makes  it  impossible to take more than a few tests
 over a short period  of time  unless many permeameters jtre used.

     Another drawback in measuring the permeabilities of clay liners is that
 the permeameter itself can be  affected by temperature changes brought on by
 the sun.  The air in the reservoir expands and causes water to flow quickly
 from the permeameter when -the  sun is out.  At the end of the day, the tem-
 perature decreases and causes  the air in the reservoir to contract, making
 the water flow back  in from  the well.  While heating and cooling effects are
 insignificant when coarse soils are involved,  measurements in compacted clays
must be averaged between both warm and cobl  hours of the day.  Tests are run
 twice because temperature related water level  fluctuations are large compared
 to water level change due to percolation.  (Bradshaw, 1986)

     One problem that occurs when testing compacted clays is that it is dif-
 ficult to ensure that the permeameter 1s working properly.  The air bubbles
 that result from displacement  by percolation are infrequent and large as they
                                    3-68

-------
 are observed in the calibrated reservoir.   A technique  has  been  developed
 which allows smaller bubbles to appear and at a more  regular  rate.   Crushed
 quartz can be-placed in the hole around the,permeameter which  reduces  the
 volume of water necessary for each increment of head  drop.  Since the  perme-
 ability of the quartz is greater than  that of the  soil, the quantity of water
 migrating from the well is the same.   (Bradshaw, 1986)

      An additional  problem arises from the influence  of atmospheric
 moisture.  Tests in compacted clays take long enough  and  involve small enough
 changes in water level  that condensation and evaporation  affect  results.
 Plastic hole covers can be used to decrease these  effects.  (Bradshaw, 1986)

      The Guelph permeameter is limited in  its usefulness, as designed,
 since the instrument is only capable of measuring  permeabilities as  low
 as  10-D cm/sec.  (Guelph permeameter product literature).   Permeabilities
 of  10-' cm/sec  have been measured experimentally using  larger  volume well
 holes (Bradshaw,  1986).  Since regulatory  requirements  for  clay  liners
 state that 10-'  cm/sec  is the maximum  permeability allowable,  it follows
 that  instrumentation should be capable of  measuring permeabilities that are
 lower than this for data to be reliable.

      Another limitation arises from the assumption that the soil being tested
 is  homogeneous  (Guelph  permeameter product literature).  This  cannot be
 easily verified under field conditions.  The  assumption does not allow for
 variations in the  clay  liner due  to large  clod  size,  for example.  If the
 test  was taken  in a clod,  the permeability might be lower than what  is
 representative  of  the liner as a  whole.

      A final drawback to testing  with  the  Guelph permeameter is the diffi-
 culty in quantifying results.   The calculations required to obtain accurate
 permeabilities  from measurements  in compacted clays are cumbersome.  There
 are standardized equations  that use simplifying assumptions (provided in the
 product literature),  but these are only  useful when greater permeabilities
 are involved.

 3.8.5.5  Ring Infiltrometers—
      In  its  simplest  form, a  ring  infiltrometer is a short length of tubing
 that  can  be  partially embedded  in soil  and filled with water.   The rate at
which  the water infiltrates  into  the soil  can be measured by recording  the
water  depth  or by keeping track of the amount of water needed  to maintain a
 constant depth within the infiltrometer.  Ring infiltrometers  can be of the
 single  or double ring type  (Figure 3-26).  The double ring infiltrometer has
a large diameter and  small diameter ring placed concentrically.  Both rings
are filled with water and, in  theory,  the water infiltrating from the outer
 ring  restricts the  lateral spread of water infiltrating  from the inner  ring.
Data from the inner ring is used to calculate the infiltration rate.

     The ASTM method for double ring  infiltrometers (D3385-76)  states that
the method is "difficult to use and the resultant data may be  unreliable  in
very coarse or heavy clay soils, or in  frozen or highly  fractured ground"
(ASTM, 1984).  In the ASTM procedure the volume of  water added  to maintain  a
                                    3-69

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      Outer ring water level
   Soil surface
                                    Scale
                                     Water leval
                                                        Inner ring
                                                                    Outer ring
                         1        Burlap (to prevent puddling)

Source: EPA/Army Corps of Engineers/USDA, 1977
                         Figure 3-26. Double-ring infiltrometer.

-------
 constant level  1n the inner ring  is  taken  as  the measure of the volume that
 infiltrates the soil.  The volume that  infiltrates over a time interval can
 be converted to an infiltration velocity expressed as  inches or centimeters
 per hour.   The  ASTM method does not  directly  yield a permeability value for
 the test soil.

      The infiltration rate (I) can be calculated from  the equation:

                                   I =  q/A

 where

      q  = volume of flow per unit  time

      A  = inside area of the ring

      The hydraulic conductivity (K)  can then  be calculated from the equation.

                                   K =  I/i

 where

      i  = hydraulic gradient.

      If the  test  is  run  until the wetting  front reaches the bottom of the
 liner then  the  hydraulic gradient is equal to the total head divided by the
 liner thickness.   Alternatively, the depth of the wetting front can be used
 in  place of  the  liner thickness.  This can be determined with tensiometers
 as  depicted  in  Figure 3-27 which is an illustration of a sealed double-ring
 infiltrometer with  two  tensiometers in place.  If the tensiometers are
 attached to  a differential pressure gauge or manometer, the passage, and,
 therefore, depth  of  the wetting front can be observed.  The hydraulic
 gradient is  found  from  the equation:

                                i  = (H + L)/L

where

      H  = depth of water above liner surface

      L  = depth of wetting front or liner thickness if break through has
    occurred.

     Sealed double ring infiltrometers,  as depicted in Figure 3-27 are the
newest development in ring inflltrometers.  In these units  the center ring is
fitted with an air-tight top.  A tube leads from the top to a flexible
plastic  bag that serves as the reservoir supplying make-up  water  to the
sealed  inner ring.  The entire inner  ring assembly is kept  completely
sub-merged within the outer ring.   Periodically, the flexible bag  is removed
and weighed to determine the water volume that has infiltrated the soil  under
the inner ring.   Submerging the sealed  inner ring  and flexible bag assures
that no pressure differences develop  between the inner and  outer  rings
(providing  the temperature is the  same).
                                    3-71

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            Sealed Inner Ring
                                                  Tensiometers
Flexible Bag
                                                        Outer Ring
     Wetting Front
^S.         /> Clay Liner
   Grout
           Figure 3-27. Sealed double-ring infiltrometer.
                             3-72

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     Ring  infiltrometers, compared to other devices, have the advantage that
 they cover a relatively large area thus subjecting a large volume of soil  to
 testing.  The conversion of the infiltration rate into a permeability value
 is based on the assumptions of one-dimensional vertical flow through the soil
 mass and a uniform advance of the wetting front.  Nolan (1983) performed a
 series of tests with a single ring infiltrometer and found that under his
 experimental conditions neither of these assumptions were strictly correct.

     The sealed double ring infiltrometer has the disadvantage of requiring
 more setup time than other types of infiltrometers.  Ring infiltrometers,
 in general require long test periods, 30 to 90 days being typical for clay
 liners and even longer periods required in some situations, for example if
 the liner has a low degree of initial saturation.  Another disadvantage
 is that very low permeabilities (less than 10~8 cm/s) cannot be accu-
 rately measured with these devices.  (Daniel, 1987)

 3.9  REFERENCES

 Acar, Y. B., and S. D. Field.  1982.  Organic Leachate Effects to Hydraulic
     Conductivity in Fine-Grained Soil, Volume 1.  Report No. GE-82/01,
     Louisiana State University.

 Aldabagh, A. S. Y., and C. E. Beer.  1971.  Field Measurement of Hydraulic
     Conductivity Above a Water Table with an Air-Entry Permeameter.
     Transactions of the American Society of Agricultural Engineers.
     14:29-31.

 Allison, L. E.  1947.  Effect of Micro-organisms on Permeability of Soil
     Under Prolonged Submergence.  Soil Science.  63:439-450.

 Anderson, D. 1983.  Effects of Organic Solvents on Clay Liners - Contaminant
     Resistant Bentonite Slurry Mixtures.  Report Prepared for U.S.
     Environmental Protection Agency, Cincinnati, Ohio, 46 pp.

 Anderson, D. C.  1981.  Organic Leachate Effects on the Permeability of Clay
     Soils.  M.S. Thesis, Soil and Crop Sciences Department, Texas A & M
     University, College Station, Texas.
                                                     «
 Anderson, D. C. and K. W. Brown.  1981.  Organic Leachate Effects on the
     Permeability of Clay Liners,  pp. 119-130.  In D. W. Shultz (ed.) Land
     Disposal:  Hazardous Waste.  EPA-600/9-81-002b.  National Technical
     Information Service, Springfield, Virginia.

 Anderson, J. L., and J. Bouma.  1973.  Relationships Between Saturated
     Hydraulic Conductivity and Morphometric Data of an Argillic Horizon.
     Soil Science Society of America Proceedings.  37:408-413.

Andrews, R. E., J. J. Gawarkiewicz, and H. F. Winterkorn.  1967.  Comparison
     of the interaction of 3 clay minerals with water, dimethyl  sulfoxide,
     and dimethyl  formamide.  Highway Research Record.  No. 209.  pp. 66-78.

ASTM.  1984.  Annual  Book of ASTM Standards, Part 19, Soil  and Rock; Building
     Stones.  American Society for Testing and Materials, Philadelphia,
     Pennsylvania.
                                    3-73

-------
 Boutwell, G. P., and R. K. Derick.  1986.  Groundwater Protection  for
      Sanitary-Landfills in the Saturated Zone.  Paper presented  at Waste
      Tech '86.  National Solid Waste Management Association,  Chicago,
      Illinois.

 Boutwell, G. P., and. V. R. Donald.  1982,  Compacted  Clay  Liners for
      Industrial  Waste Disposal.  ASCE National Meeting,  Las Vegas.  Nevada,
      April 1982. 23 p.

 Bouwer, H.  1978.  Groundwater Hydrology.  McGraw-Hill Book Company, New
      York, New York.  480 pp.

 Bowles, J. E.  1979.  Physical  and Geotechnical  Properties of Soils.
      McGraw-Hill  Book Company,  New York.   478  pp.

 Boynton,  S.  S.,  and D. E.  Daniel.   1985.   Hydraulic Conductivity Tests on
      Compacted Clay.  J. of Geotechnical  Engineering.  111(4):465-478.

 Bradshaw,  K. L.,  1986.  An Assessment  of  the Standard Percolation Test.
      Masters Thesis.  University  of Waterloo,  Waterloo, Ontario.

 Brown,  K.  W., J.  Green,  and J.  Thomas.   1982.  The Influence  of  Selected
      Organic Liquids on  the Permeability  of Clay Liners  (draft).  Texas
      Agricultural  Experiment Station,  Soil and Crop Science Department,
      College Station,  Texas.

 Bryant, J.,  and A .  Bodocsl.  1986.  Precision and Reliability of Laboratory
      Permeability Measurements, EPA-600/2-86-097, U.S. Environmental
      Protection Agency,  Cincinnati,  Ohio.  177 pp.

 Chen, H. W.,  and  L.  0. Yamamoto.   1987.   Permeability Tests for  Hazardous
      Waste Management  Unit Clay Liners.   In:   Geotechnical and Geohydrologi-
      cal Aspects  of  Waste  Management.  D.  J. A. van Zyl et al. eds.  Lewis
      Publishers,  Inc., Chelsea, Michigan,  pp. 229-243.

 Daniel, D. E. 1987.  Hydraulic Conductivity Tests for Clay Liners.  In:
      Ninth Annual  Symposium on  Geotechnical and Geohydrological  Aspects of
      Waste Management.   Colorado State University, Fqrt Collins, Colorado.

 Daniel, D. E. 1981.  Problems  in  Predicting the Permeability of Compacted
      Clay  Liners.  In:   Symposium  on Uranium Mill Tailings Management,  Fort
      Collins, Colorado,  pp. 665-675.

 Daniel, D. E., D.  C. Anderson,  and S. S. Boynton.  1985.  Fixed-Wall vs.
      Flexible-Wall Permeameters.   In:  Hydraulic Barriers for Soil  and  Rock,
     ASTM  STP 874, American  Society for Testing and Materials, Philadelphia,
     Pennsylvania,   pp.  107-123.

Daniel, D. E., S. J. Trautwein, S. S. Boynton,  and D.  E.  Foreman.  1984.
     Permeability Testing with Flexible Wall  Permeameters.   Geotechnical
     Testing Journal.  7(3):113-122.

Dunn, R. J.,  and J. K. Mitchell.  1984.  Fluid  Conductivity Testing of  Fine
     Grained Soils.  J. of Geotechnical Engineering.   110(11):1648-1665.
                                    3-74

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Griffin, R. A., G. L. Herzog, T. M. Johnson,  W.  J.  Morse,  R.  E.  Hughes,
     S. F. J. Chou, and L. R. Folmer.  1985.   Mechanisms of Contaminant
     Migration Through a Clay Barrier -- Case Study,  Wilsonville,  Illinois.
     In:  Land Disposal of Hazardous Waste:   Proceeding of the Eleventh
     Annual Research Symposium.  (EPA/600/9-85-013)   U. S. Environmental
     Protection Agency, Cincinnati, Ohio.  pp. 27-38.

Haji-Djafari, S., and J. C. Wright.  1982.  Determining the Long-Term  Effects
     of Interactions Between Waste Permeants  and Porous Media.   Presented at
     American Society for Testing and Materials  Second Symposium on  Testing
     of Hazardous and Industrial Solid Wastes.  26  p.

Hansbro, S.  1960.  Consolidation of Clay with Special Reference to  the
     Influence of Verticle Sands Drains.  In:  Proceedings 18, Swedish
     Geotechnical Institute, Stockholm, Sweden.

Herzog, B. L. and W. J. Morse.  1984.  A Comparison of Laboratory  and  Field
     Determined Values of Hydraulic Conductivity at a Waste Disposal Site.
     In:  Seventh Annual Madison Waste Conference Proceedings.   University of
     Wisconsin Extension, Madison, Wisconsin,  pp.  30-52.

Holtz, R. D., and W. D. Kovacs.  1981.  An Introduction to Geotechnical
     Engineering.  Prentice-Hall, Englewood Cliffs, New Jersey.  733 pp.

Horton, R., M. L. Thompson, and J. F. McBride.  1987. Method of Estimating
     the Travel Time of Noninteracting Solutes Through Compacted Soil
     Material.  Soil Sci. Soc. Am. J. 51(l):48-53.

Johnson, A. I.  1954.  Symposium on Soil Permeability. ASTM  STP 163,
     American Society for Testing and Materials, Philadelphia, Pennsylvania.
     pp. 98-114.

Klute, A.  1965.  Laboratory Measurement of Hydraulic Conductivity of
     Saturated Soil.  In:  Methods of Soil Analysis,  C. A. Black,  Ed.
     Amer. Soc. of Agronomy, Madison, Wisconsin, pp. 210-220.

Knight, R. B., and J. P. Haile, 1984.  Construction of the Key Lake  Tailings
     Facility.  In Proceedings of the International  Conference on  Case
     Histories in Geotechnical Engineering.   St. Louis, Missouri.

Lambe, T. W.  1955.  The Permeability of Fine-Grained Soils.  ASTM 163,
     American Society for Testing and Materials, Philadelphia, Pennsylvania.
     pp. 55-67.

Lambe, T. W., and R. V. Whitman.  1979.  Soil Mechanics, SI Version.
     John Wiley and Sons, Inc., New York.  553 pp.

Lee, D. Y. and R. J. Suedkamp.  1972.  Characteristics of  irregularly  shaped
     compaction curves of soils.  Highway Research  Record, No. 381,  p. 1-9.

Luxmoore, R. J., B. P. Spalding, and I. M. Munro.  1981.   Area!  Variation and
     Chemical Modification of Weathered Shale Infiltration Characteristics.
     Soil Science Society of America Journal. 45:687-691.
                                    3-75

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 Mason, D. D., J. F. Lutz, and R. G. Peterson.  1957.   Hydraulic Conductivity
      as Related to Certain Soil Properties in a Number of Great Soil  Groups-
      Sampling Errors Involved.  Soil Science Society  of America Proceedings.
      21:554-561.

 Matyas, E. L.  1967..  Air and Water Permeability of Compacted  Soils:
      Permeability and Capillarity of Soils.  Standard Technical  Publication
      417, ASTM, Philadelphia, Pennsylvania,  pp. 160-175.

 Mitchell, J. K.  1976.  Fundamentals of Soil  Behavior.   John Wiley and Sons,
      New York.  422 pp.

 Mitchell, J. K., and J. S. Younger.  1967.  Abnormalities  in Hydraulic Flow
      through Fine-Grained Soil.  ASTM STP  417.   pp. 106-139.

 Mitchell, J. K., D. R. Hooper,  and R. G. Campanella.   1965.  Permeability of
      Compacted Clay.  Journal  of the Soil  Mechanics and  Foundation Division,
      ASCE.  91:41-66.

 Nolan,  T. W.  1983.  Evaluation of the Single-Ring  Infiltrometer for
      Measuring Hydraulic  Conductivity of Soil Lines.  Masters Thesis.
      Syracuse University,  Syracuse,  New York.   93 pp.

 Oakes,  D.  J.  1960. Solids Concentration  on Effects  in Bentonite Drilling
      Fluids.  Clay  and  Clay Minerals.   8:252-273.

 Olson,  R.  E.,  and D. E. Daniel.   1979.  Field and Laboratory Measurements
      of the  Permeability  of Saturated  and  Partially Saturated Fine-Grained
      Soils.   In:  ASTM  Symposium  on  Permeability and Groundwater Contaminant
      Transport,  Philadelphia, Pennsylvania.  67 pp.

 Peirce, J. J.  and K. A. Witter.   1986.  Termination Criteria for Clay
      Permeability Testing.  ASCE  Journal of Geotechnical Engineering,
      September 1986.   112(9):841-854.

 Petsonk, A.  M., W.  Romanowski, and V.  Richards.  1987.  Field Permeability
      Testing  for a  RCRA Landfill  Final Cover.   In:  Proceedings of Hazmacon,
      87.  Santa Clara, California.  April 22.

 Peyto?Ao~* R" J' P< Gibb' M' H*  LeFalvrei,  J. D. Burch, and M.  J. Barcelona.
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      Remedial  Action, Incineration and Treatment of Hazardous Waste -
      Proceedings of the Twelfth Annual Research Symposium.  (EPA/600/
      9-86/022)  U.S. Environmental Protection Agency,  Cincinnati, Ohio.
      pp. 21-28.

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Sangrey, D. A., D. K. Noonan,  and G. S. Webb.  1976.  Variation in  Atterberg
      Limits of Soil  Due to Hydration History and Specimen Preparation. Soil
     Specimen Preparation for Laboratory Testing, ASTM STP 599,  American
     Society for Testing and Materials,  pp. 158-168.
                                    3-76

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Smith, R. M., and D. R. Browning.  1942.  Persistent Water-Unsaturation of
     Natural -Soil in Relation tq Various SoiJ and Plant Factors.   Soil
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Sowers, G. B., and G. F. Sowers.  1970.  Introductory Soil  Mechanics and
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     Water Monitoring Review.  Fall, pp. 131-138.

Truesdale, R. L., L. Goldman, J. Peirce, B. Cox, K. Witter, and T. Peel.
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     Engineering, Vol. 2, Stockholm, Sweden,  pp. 403-406.


                                    3-77

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                                  CHAPTER 4

              CLAY-CHEMICAL  INTERACTIONS AND SOIL PERMEABILITY


      It  has  been  known  for  many years  that the permeability of clay soils may
 be  drastically  altered  by chemicals present in the permeating liquid.  Apart
 from  the many recent  studies  stemming  from concern over the effects of haz-
 ardous waste and  waste  leachates  on clay liners, much research has been
 carried  out  over  the  last several decades to determine the effects of various
 chemicals  on agricultural soils or on  geological formations important for oil
 production.   The  potential  effects of  certain organic fluids on clay perme-
 ability  were recognized as  early  as 1942, when Macey's experiments with
 fireclay showed that  the rates of flow for certain organic liquids through
 clay  were  "of an  enormously higher order than for water" (Macey, 1942).
 Since Macey's experiments,  many researchers have investigated the effects of
 organic  and  inorganic fluids  on clays  in an effort to elucidate the causes of
 the observed changes  in permeability.

      The current  state  of the knowledge in this area is complicated by the
 dilemma  of how  to measure the permeability changes that appear to be caused
 by  clay-chemical  interactions.  The question of what types of permeameters
 give  valid measures of  clay-chemical compatibility remains an important
 issue.   Because permeability  studies with different fluids have been carried
 out with different test protocols, different test devices, and different
 clays, quantitative data comparisons cannot be made except in a few of the
 more  recent  studies.  Much  can be learned from a review of the research that
 has been carried  out, however, and qualitative statements can be made regard-
 ing the  behavior  of certain clays in the presence of many types of fluids.
 Unifying theories of  soil physics that explain the reported findings have
 been  advanced by  several researchers.  Such theories are useful for predict-
 ing clay-chemical incompatibilities that could lead to performance failures
 in  clay-lined hazardous waste disposal facilities.

      This  chapter presents  the experimental findings that pertain to the
 effects  of chemicals  on clay  barrier permeability as well as the theories and.
 mechanisms proposed to  explain the observed effects.  Section 4.1 defines the
 terms most important  in clay-chemical  compatibility testing— permeability
 (or,  if  the  permeating  liquid is  water, hydraulic conductivity) and intrinsic
 permeability.   Section  4.2  is a discussion of the clay-chemical interactions
 that  influence  soil permeability.  A summary of the relevant permeability
 studies  is presented  in Section 4.3.  Approaches that have been used in
 studies  to determine  clay-chemical compatibility and problems associated with
 different  test methods are addressed in Section 4.4.  Section 4.5 reviews in
more detail permeability testing  efforts that have been carried out to
measure  clay-chemical  interactions.
                                     4-1

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 4.1  PARAMETERS DETERMINED IN PERMEABILITY TESTING  FOR COMPATIBILITY

      When results of clay-chemical  compatibility  tests are compared, it is
 important to understand the parameters  that are being measured and calcu-
 lated.   The parameter usually determined  in compatibility tests is permea-
 bility,  K, which is defined by Darcy's  Law as  expressed  in Equation (4.1):

                                   K = Q/Ai                              (4.1)

 where

      Q = volumetric flow rate (L3/t)
      A s cross-sectional  area of  flow (L2)
      1 = hydraulic gradient (dimensionless).

 K  has units of  length per unit time (e.g., cm/s).   The density and viscosity
 of the permeating liquid  as well  as the pore size distribution within the
 soil  matrix will  influence the value of K.  Hydraulic conductivity refers to
 the value of K  when the permeating  fluid  is water.  Darcy's Law is limited to
 saturated soil  conditions and to  laminar  flow  conditions.

      In  order to  separate the effects of  the liquid properties (viscosity and
 density)  from those of the medium (pore size distribution), a different
 parameter,  the  intrinsic  permeability, should  be used.   Intrinsic permeabil-
 ity,  usually referred to  as k,  is a property of the medium that is dependent
 on  the shape, size,  and continuity  of the pore spaces.   Intrinsic permeabil-
 ity is "a measure  of the  relative ease with which a porous medium can trans-
mit a liquid  under a potential  gradient. ! It is a property of the medium
alone and 1s  independent  of the nature of the  liquid and of the force field
 causing movement"  (Lohman  et  al., 1972).

      Intrinsic  permeability,  k, has units of length squared (e.g., cm2)  and
Is  related  to permeability, K, by Equation (4.2):


                   K  *  k £ g          or          k = Kpg               (4'2)

where                                                »

     p = density of  the fluid  (M/L3)
     u a dynamic viscosity  of the fluid (M/Lt)
     g = acceleration due to gravity (L/t2).

     In clay-chemical  compatibility testing,  the value of K for a  clay  soil
permeated by a certain  chemical is determined  from measurements of the  fluid
Inflow or outflow.  A  change or lack of change  in  the value of K (when  com-
pared to K for water or other baseline fluid) may  be due to a combination  of
two factors—
                                     4-2

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      9  Difference in the permeant fluid viscosity and density (compared to
         baseline permeant fluid)

      o  Change in porous medium characteristics as a result of clay-chemical
         interactions.

      In order to separate these effects, it is usually necessary to report
 the results of the tests in terms of intrinsic permeability (k)  both for
 the tests with the baseline permeant fluid and for the tests with the chemi-
 cal permeant fluid in question.  In practice,  most researchers report and
 discuss their test results in terms of permeability (K)  rather than intrinsic
 permeability (k).  Provided the density and viscosity of the test fluid  (at
 the test temperature) are known, one could calculate k to correspond to  each
 K value reported.  In general,  only substantial  permeability changes are
 meaningful  in clay-chemical  compatibility  testing.  When large changes in
 permeability are measured during the course of a test,  the clay-chemical
 interaction is apparent  regardless  of whether  the k values are computed  and
 plotted.

 4.2  CLAY-CHEMICAL INTERACTIONS THAT INFLUENCE PERMEABILITY

      Mechanisms whereby  the  chemical  nature of a permeant fluid may alter
 clay soil  permeability and theories to predict clay-chemical  interactions
 have been  described by several  researchers,  among them Mitchell  (1976),
 Brown and  Anderson (1980), Acar and Field  (1982),  Evans,  Chaney,  and Fang
 (1981),  Anderson and  Jones (1983),  Daniel  (1982,  1983),  Daniel and
 Liljestrand (1984), Dunn  (1983),  Monserrate (1982),  Peirce (1984),  and
 Griffin  and Roy (1985).   In  addition to laboratory and field permeability
 tests, methods such as X-ray diffraction,  shrink-swell measurements,  settling
 tests, and  other techniques  have been  used to  investigate the clay-chemical
 interactions that influence  permeability.

      Changes in the permeability of clay soils due to  chemical  interactions
 may result  from--

      •   Alterations in soil  fabric  stemming  from chemical  influences
         on  the diffuse double layer surrounding  clay particles

      •   Dissolution of soil  constituents by  strong  a&ids  or  bases

      •   Precipitation  of  solids  in  soil  pores

      t   Soil pore  blockage due  to the  growth of microorganisms.

      The permeability  of a soil may also be affected by the pore fluid veloc-
 ity;  high velocities can displace small particles  in the  soil matrix.  The
 fluid flow velocity can also influence  chemical interactions that depend on
 the time of  contact between the soil and some chemical component of the
permeating fluid.  Thus,  permeability and fluid flow velocity are inter-
 related characteristics of a soil-permeant fluid system.
                                    4-3

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4.2.1  Son Fabric and Permeability

     The permeability of any soil depends upon the geometric characteristics
of the area available for fluid flow.  Influencing factors are the size,
shape, tortuosity, and degree of interconnection between the pore spaces.
The geometric arrangement of the soil particles will determine these pore
space characteristics.

     The term "fabric" refers to the arrangement of particles, particle
groups, and pore spaces in a soil.  Modes of particle association orienta-
tion in clay suspensions were described by van Olphen (1963) as "dispersed,"
"aggregated," "flocculated," or "deflocculated" (see discussion in
Section 2).  Particle associations corresponding to these descriptors are
illustrated in Figure 2-10.  Dispersion and flocculation represent the ex-
tremes in soil fabric classification, and a chemical present in the permeat-
ing liquid may influence the permeability of a clay soil by altering the  soil
fabric toward either of these extremes.  Figure 4-1 illustrates how a change
in pore diameter can drastically alter permeability.

     A dispersed deflocculated soil fabric tends to have a large number of
very small pore spaces; with flocculation, relatively large-sized inter-
particle and interaggregate pores are formed.  These large diameter pores
can cause drastic changes in the permeability of the clay soil since the
flow rate is proportional to the square of the diameter of the flow channel.

     The pulling together of groups of clay particles into aggregates results
when cohesive forces between individual clay particles outweigh the repulsive
forces.  The forces of attraction result from London-van der Waals forces  and
do not vary significantly with the chemistry of the pore water.  Attractive
forces are strongest close to the clay surface and diminish rapidly with
increasing distance from the surface.

     The forces of repulsion between adjacent clay surfaces, however, are
primarily electrostatic and are influenced by the clay surface charge and  the
chemistry of liquid adjacent to the clay surfaces.  Interparticle spacing  is
a function of the thickness of the diffuse double-layer cationic clouds that
form the Gouy layer of the diffuse double layer (Anderson and Jones, 1983).
(See also Section 2.3 and discussion below).  In theory, the direction of
change in permeability associated with varying pore f-luid chemistry could  be
predicted if the variables that affect the thickness of the diffuse double
layer are known (Acar and Seals, 1984).  However, the heterogeneous mineral
composition and wide particle-size distribution common in many soils along
with the complicated nature of chemical-soil Interactions make this difficult
to accomplish in practice.

4.2.1.1  Diffuse Double-Layer Theory—
     The theory of the diffuse double layer (also called the electrical
double layer) has evolved from the studies of colloid chemistry directed
at the description of surface interactions of small particles in a water-
electrolyte system.  The description that follows 1s excerpted from Mitchell
(1976, pp. 112-113).

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Source: Anderson, 1981
            Figure 4-1. Change in a pore diameter (400%) corresponding
                     to a permeability increase of 25,600%.
                                   4-5

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      In a dry clay, adsorbed cations are tightly  held  by  the  negatively
      charged clay surfaces.  Cations in excess  of those needed  to neutralize
      the electronegativity of the clay particles  and their associated anions
      are present as salt precipitates.  When  the  clay  is  placed  in water the
      precipitated salts go into solution.  Because the adsorbed  cations are
      responsible for a much higher concentration  near  the surfaces of par-
      ticles, there is a tendency for them to  diffuse away in  order to equal-
      ize concentrations throughout.   Their freedom to  do  so,  however, is
      restricted by the negative electric field  originating in the particle
      surfaces . . . The negative surface and  the  distributed  charge in the
      adjacent phase are together termed the DIFFUSE DOUBLE LAYER . . .

      The distribution of cations adjacent to  a  negatively charged clay
 particle in suspension (the diffuse  double layer)  is depicted in Fig-
 ure 4-2 (see also Figure 2-6).   The  distribution  for a particular soil-
 water-electrolyte system results from a balance between the tendency of the
 cations to escape due to diffusion, and the opposing electrostatic attraction
 of the  clay surface for the cations.   The Gouy-Chapman theory of the diffuse
 double  layer (Gouy, 1910;  Chapman, 1913)  is widely recognized, and mathe-
 matical  descriptions  of the diffuse  double layer  have  been formulated for
 both planar and spherical  surfaces.

      Despite the fact that the  Gouy-Chapman theory does not account for all
 the factors that can  influence  the behavior of the  soil-water-electrolyte
 system,  it has  been useful  as a generalized model  for  explaining clay-
 chemical  interactions that affect permeability.  Since the thickness of the
 double  layer influences  the level of  interlayer and interparticle repulsion,
 system  variables that influence the double-layer thickness consequently
 affect  the physical interactions among  clay particles.

      The  nature  and thickness of the double layers, and thus the repulsive
 forces, depend  upon characteristics of  clay particles and the pore fluid.
 In  general,  the  tendency for particles  in  suspension to flocculate decreases
with  increased  thickness of the double  layer.  An approximate quantitative
 indication  of the  relative  influences of  several factors on the thickness of
 the double  layer is given  by Equation  (4.3) below  (see Mitchell, 1976,
 p.  118):
                           H,  -DkT
                                8;
where
     H » thickness of the double layer
     D » dielectric constant of the medium
     k * Boltzman constant (1.38 x 10~16 ;erg/K)
     T » temperature in degrees Kelvin
                                     4-6

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             ©

              (S)
©   ©
-  © ©

                                                        Disianc*
 Figure 4-2. Distribution of ions adjacent to a clay surface according
             to the concept of the diffuse double layer.
                                4-7

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     no = electrolyte concentration

      e » unit-electric charge,  16 pvp  10~6  coulomb

      v = valence of cations  in  the  pore  fluid.

      The thickness  varies  inversely with the valence of the cations present:
 and inversely with  the square  root  of  the concentration; the thickness
 increases with the  square  root  of the  dielectric constant and the tempera-
 ture,  other factors remaining  constant.   Bas.ed on the Gouy-Chapman model,
 Lambe  (1958)  noted  that the  following  variables in the soil-water system
 affect double-layer thickness and colloidal stability:  dielectric constant,
 electrolyte concentration, temperature,  ionic valence, size of hydrated ions
 present,  pH,  and anion adsorption.

      It has been found that  attractive forces exceed repulsive forces when
 interlayer spacing  is  about  0.5 nm.  (Yong and Warkentin, 1975).  Thus, a
 sufficient reduction in repulsive forces (i.e., reduced double-layer
 thickness)  could "transform  a massive, structureless, and slowly permeable
 clay barrier into an aggregated, structured, and more permeable barrier"
 (Anderson and Jones,  1983).

     4.2.1.1.1   Dielectric Constant—The dielectric constant is a measure of
 the  ease  with which molecules can be polarized and oriented in an electric
 field  (Mitchell,  1976,  p. 113).  It represents the ability of a fluid to
 transmit  a  charge.   Quantitatively, the  static dielectric constant is defined
 by D 1n Coulomb's equation (Equation 4.4), where F is the force of electro-
 static  attraction between two charges, Q  and Q1, separated by a distance d.





     As the dielectric  constant decreases, the fluid film surrounding the
 clay that contains  positive  cations must  be thinner for the negative surface
 charge on the clay  to be neutralized.  For a constant surface charge, the
 surface potential function will increase  as the dielectric constant de-
 creases.  Since most organic liquids have dielectric constants substantially
 lower than water, it is to be expected that the double-layer thickness would
be reduced  (with an associated tendency toward flocculation) when an organic
 liquid rather than water surrounds the clay particle.  Due to the effects of
dielectric constant on  the electrical  double layer,  there 1s a relationship
between the dielectric  constant of an adsorbed fluid and interlayer spacing
exhibited by clay particles.  In general, interlayer spacing decreases with a
decrease  1n the dielectric constant, although this apparent relationship can
be complicated by the other .factors that affect interlayer spacing.

     4.2.1.1.2  Electrolyte Concentration—As the  electrolyte concentration
in the pore fluid increases,  the thickness of the  double layer tends to
decrease, promoting flocculation.  An analysis of  the effect of electrolyte
concentration on the double  layer indicates that an  increase 1n concentration
                                     4-8

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 reduces  the  surface potential for the condition of constant surface charge.
 Also,  the dec_ay of potential with distance is more rapid with increased
 electrolyte  concentration.  In essence, the double layer is suppressed by an
 increase in  electrolyte concentration.  Interparticle interactions extend to
 much greater particle spacings for a low electrolyte concentration (e.g.,
 0.83 x 10~4  M NaCl) than a higher concentration (e.g., 0.83 x 10~2 M
 NaCl)  (Mitchell,  1976, p. 122).  The effect of salt concentration on the
 behavior of  clays has been discussed by Anderson (1981):

     As  salt concentration in interparticle spaces increases, the
     cationic cloud is compressed closer to the clay surface, resulting in a
     decrease in  electrostatic repulsion and interlayer spacing.  Weiss
     (1958)  noted the direct relationship between salt concentration and
     interparticle spacing in smectitic clay minerals in a study using
     distilled water and several concentrations of sodium chloride in water.
     Both distilled water and 0.01 N NaCl gave infinite interlayer spacing
     values  (the  clay was completely dispersed), while 1.0, 3.0, and 5.0 N
     NaCl gave interlayer spacings of 0.93, 0.61, and 0.58 nm, respectively.


     4.2.1.1.3  Temperature—An increase in temperature causes an increase
 in double-layer thickness with a corresponding tendency toward dispersion.
 However, the value of the dielectric constant for various fluids is also
 affected by  temperature, generally decreasing with increased temperature.
 For water, the value of the product DT (Equation 4.3) is reasonably constant,
 and temperature effects tend to cancel  out.

     4.2.1.1.4  Ionic Valence—The cation valence affects both the surface
 potential and the thickness of the double layer.  For solutions of the same
molarity and a constant surface charge, increasing the cation valence will
 cause a decrease  in the thickness of the double layer and a tendency toward
 flocculation.  It is also shown that an increase in valence will  suppress the
midplane concentrations between parallel  plates, leading to a decrease in
 interplate repulsion (Mitchell, 1976, p. 122).

     4.2.1.1.5  Size of Hydrated Ions—The smaller the size of the hydrated
 ion, the closer it can approach the surface of the clay particle (Lambe,
 1958).  Thus, for a given cation valence, the thickness of the double layer
will tend to decrease with decreasing hydrated radii "of double-layer cations.

     4.2.1.1.6  p_H~Changes in pH can affect the thickness of the double
 layer in several  ways.  The electrolyte concentration as well  as the net
negative charge on the clay particle are influenced by the solution pH.  The
formation of stable suspensions or dispersions of clay particles often
require high pH conditions.  There are  two ways in which pH can change the
surface charge that results from chemical  reaction at the surface of the clay
particles.    First, a high pH can cause dissociation  of hydroxyl  groups at
the edge of clay particles, increasing  the net charge and expanding the
double layer.  The dissociation reaction is given below:


                                 H2°      -    +
                           SiOH ——>  SiO  + H+                        (4.5)
                                     4-9

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 The higher ths pH,  the greater the  tendency for the H+ to dissociate and
 the greater the effective negative  charge.  Low pH discourages this
 dissociation,  lowering the surface  charge, reducing the thickness of the
 double layer,  and promoting flocculation  (Evans et al., 1981; Mitchell. 1976,
 p.  127).

      Second, pH affects alumina exposed at the edges of clay particles.
 Alumina ionizes positively at  low pH and  negatively at high pH.  Thus, in an
 acid environment, positive double layers  may develop at the edges of clay
 particles  with H+ serving as the potential determining ion (Mitchell,
 1976,  p.  126).

      Changes in pH  do  not significantly affect surface charge resulting from
 isomorphous substitution of the crystal lattice of the clay mineral.  Thus,
 clays  with most of  their surface charge attributed to Isomorphous substitu-
 tion (e.g., smectites  and mites)'are less affected by changes in pH than
 the kaolinite  minerals,  which  have  most of their surface charge resulting
 from surface chemical  reactions (see Section 2.3).


     4.2.1.1.7  Anion  Adsorption—Adsorption of anions (e.g., Cl~s PO/p3
 and certain surfactants)  by the clay particle can increase the net negative
 charge and increase the  double-layer thickness.  Dispersion can occur as a
 result.

 4.2.1.2  Displacement  of Water—
     If adsorbed water within  clay  particles is displaced by a fluid with a
 different  dielectric constant  or electrolyte concentration, the result may be
 a change 1n the interlayer spaces of the  clay.  Such changes can cause the
 clays  to shrink and crack.   This can result 1n the formation of large
 conducting channels through  the soil along with drastic increases in the
 permeability.   Desiccation  of  clays by certain organic fluids has been
 reported by Anderson (1981)  and others.

 4.2.1.3  Cation  Exchange-
     Cations adsorbed  in  the diffuse double layer are exchangeable with other
 cations in  solution.   In  general, the affinity of a cation for a clay
 Increases with  cation  valence  arid decreases with increasing ionic radius
within an  element group.   (See  Section 2.2.)

     Cation exchange will  usually result  in a change in double layer
 thickness.  The  thickness of the double layer decreases with  increasing
 cation valence  for montmorillonite;  replacement of Na+ with Ca++ results
 1n a reduction of interlayer basal  spacing from over 4 nm to  about 1.9 nm.
 For montmorillonite, only two  layers of water are incorporated between layers
when calcium is  the adsorbed cation; with sodium,  the number  of water layers
between layers  is practically  unlimited. ; Thus, cation exchange can cause
double-layer collapse, desiccation and shrinkage,  flocculation,  and increased
permeability for certain clays.

     Theng  (1974) has summarized the Importance of cation  exchange in
clay-organic complexes:
                                    4-10

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      .  .  . Since uncharged polar organic molecules are adsorbed essen-
      tially by replacement of the interlayer water, the behavior of such
      molecule's is likewise strongly influenced by the exchangeable cation.
      Evidence is accumulating to show that, at least at low water contents,
      cation-dipole interactions are of paramount importance in their effect
      on the adsorption of polar organic species by clay materials.

4.2.2 Dissolution by Strong Acids or Bases

      Both organic and inorganic acids react with and dissolve aluminum,
iron, and silica in the crystal lattice of clay minerals.  Strong bases can
have  a similar effect.  This dissolution can result in a release of mineral
fragments that may migrate from their original position and leave enlarged
pore  spaces for conducting the permeant fluid through the clay.  Anderson
and Jones (1983) have pointed out that "whether the permeability of the
clay  barrier increases or decreases will depend on the fate of the migrating
particles."  The increase in conducting pore size may give rise to an
increased permeability if the particles migrate through the clay mass.  If
the particles lodge in pore constrictions, clogging the conducting pore
spaces, a decrease in permeability may result (Anderson and Jones, 1983).

      Data originally reported by Pask and Davies (1945) show that sulfuric
acid  dissolves 3, 11, and 89 percent of the aluminum present in kaolinite,
illite, and smectite.  Other studies also suggest that kaolinite is less
soluble than smectite in strong acids (Grim, 1953).

4.2.3  Precipitation of Solids

      The precipitation of solids in the soil-water system is controlled by
ionic concentration and equilibrium solubility.  If the concentration of
certain ions exceeds the solubility limits, minerals such as gypsum
(CaS04 2H20) or jarosite (KFe3(S04)2(OH)6) may precipitate from solution
(Shepard, 1981; Dunn, 1983).  Formation of such precipitates can clog
pore  spaces in the soil matrix.

4.2.4  Effect of Microorganisms

     The presence of microorganims can affect the mobility of fluids
through the soil.  Fuller (1974) classified activity-of microorganisms in
terms of three classes of chemical reactions:  (1)  oxidation and reduction,
(2) mineralization and immobilization, and (3) reactions with organic consti-
tuents.  In certain circumstances, the attenuation of contaminants in soils
is drastically affected by microorganisms.  Processes that can contribute to
attenuation of contaminants by microorganisms include the following (Fuller,,
1974; Dunn, 1983):

     o  Degradation of carbonaceous wastes

     o  Transformation of cyanide to mineral nitrogen and denitrifi-
        cation to nitrogen gas
                                    4-11

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      •    Oxidation-reduction  reactions With metal  ions

      •    Reduction of sulfate to  sulfide

      •    Production of carbon dioxide from organic molecules

      •    Production of simple organic acids

      •    Production of humic  and  fumaric  acids  that  can react with
           trace contaminants

      •    Production of organic species on which trace contaminants
           can  be adsorbed.

      Apart from the benefits of attenuation, the physical presence of the
microorganisms as well  as the  gases produced as a result of the reactions
listed above can cause  blockage in the conducting pore spaces within soils,
reducing  the area for flow and decreasing  permeability.  This effect has been
noted 1n  permeability tests, particularly  when the  permeant fluid is
conducive to the growth  of microorganisms.

 4.3   MEASURING CLAY-CHEMICAL  COMPATIBILITY THROUGH PERMEABILITY TESTING

      Permeability is  a  highly  variable engineering property of soils, and
slight  changes  in the measurement technique or test equipment can cause
order of  magnitude  changes in  the values determined (Mitchell  et al.,
1965).  Because one  is always  dealing with orders of magnitude in perme-
ability testing,  it  is unrealistic to expect test results to agree within
less  than  several hundred percent (Zirnnie  et al., 1981).  Bryant and Bodocsi
(1986)  have also  examined precision and reliability that can be achieved in
laboratory permeability measurements.  No widely accepted method exists for
measuring  clay-chemical compatibility through permeability testing.  Thus,
a variety  of equipment and techniques have been employed in this area of
research.  Some of  the variables in test methods are described 1n this
section,  and advantages and disadvantages  are highlighted.  For additional
information and recommendations see Bowders et al.  (1986).

4.3.1  Measurement  Devices

      The  permeability of clay  soils to various liquids is usually deter-
mined  in  either constant head  or falling head tests in fixed-wall, flexible-
wall, or  consolidation permeameters. Each  category of test device can have
many  variations.  Fixed-wall permeameters  that have been used in clay-
chemical  compatibility testing  include stainless steel permeameters, plexi-
glass permeameters, thick-walled pyrex glass permeameters, glass cylinders,
PVC (polyvinyl   chloride) tubes, and shrink tubing.  Shrink tubing may, in
fact, lend to fixed-wall tests a major desirable feature of flexible-wall
tests—reduction  in the possibility of sidewall leakage.

     Tests with water and other solutions that do not interact with clays
have  shown that comparable permeability measurements may be obtained
through different types of test devices.   Everett (1977)  measured the perme-
ability of Lacustrine clays in falling head tests over a 2-month test period
1n three types  of fixed-wall  permeameters;.   Test results showed almost
                                    4-12

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equivalent permeability readings in all test devices.  Values measured
were 9.0 x IQj9 cm/s in a commercial metal permeameter, 6.9 x 10~9 cm/s
in PVC pipe, and 8.3 x 10~9 cm/s in shrink tubing.

     Permeability tests performed in both fixed-wall and flexible-wall tests
at Duke University (Peirce, 1984; Peirce and Peel, 1985) also indicate that
comparable data can be obtained from the different devices.  Test fluids used
in the Duke investigation did not significantly alter the soil permeabilities
as compared to baseline permeabilities obtained with 0.01 N calcium sulfate.,
More than 100 tests were carried out.  The reproducibility of the permeabil-
ity results suggests that side-wall leakage in fixed-wall devices can be
virtually eliminated through careful quality control during sample prepara-
tion, compaction, and testing if the permeant fluid does not alter the clay
that is tested.

     Test results may differ somewhat with different types of permeameters
when the test fluid is other than water (or comparable baseline fluid).
Daniel (1983) found that methanol in tests with kaolinite in three types of
permeameters produced similar curves (permeability versus pore volumes passed
through sample) but with compaction mold permeabilities somewhat higher than
values measured in flexible-wall or consolidation cells.

4.3.2  Test Setup

     Whether permeability tests are carried out as constant head or falling
head should not affect the validity of the test results.  Effectively, one is
doing the same thing in both tests.  In the constant head test, readings are
converted to a flow rate; in the falling head test, readings are converted to
changes in head.  Most of the permeability tests described in this section
are essentially constant head tests because of the very low permeabilities of
compacted clay soils.  Test results reported by Monserrate (1982), however,
were computed as falling head permeabilities.

     Buettner and Haug (1983) noted that leakage is the controlling factor on
how low a permeability can be measured.  They measured total leakage from
their flexible-wall permeameter setup by placing a solid metal block in the
cell and monitoring the changes in inflow and outflow.  Volume change in-
dicators with an accuracy of +0.005 cm3 were used to determine the leak-
age rate and also enabled the researchers to measure"the change in volume of
clay soils due to consolidation or swelling.  Buettner and Haug found that
if leakage is not corrected for, the potential error at low permeabili-
ties (less than 10~12 cm/s) can be as high as 2 orders of magnitude.

4.3.3  Compatibility of Materials with Test Fluids

     A problem that has become apparent in testing organic fluids in triaxial
cells is the incompatibility between the commonly used latex membranes and
the fluid to be tested (Acar et al., 1984a; Foreman and Daniel, 1984).
Excessive deformations (i.e., wrinkling and expansion) in the membrane may
occur with possible effects on the test results.  One technique used by
                                    4-13

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 Acar et al. (1984a) to alleviate problems resulting from incompatibility was
 to wrap the samples with two rounds of 0.03-mm sheet Teflon®.   After  place
 ment around the wrapped samples, the membranes were coated  with a
 contaminant-resistant (silicon base) grease to decrease  chemical diffusion.
 Even with these provisions, however, acetone used as the test  fluid was found
 to diffuse through the membrane into the: cell  water.  A  procedure and
 apparatus that can be used to test the membrane-permeant fluid compatibility
 have been described by Rad and Acar (1984).

      Foreman and Daniel  (1984) also found a workable technique to be  wrapping
 the soil  sample along with the top cap and base pedestal  with  two or  three
 revolutions of 15-cm (6-inch) -wide Teflon® tape before  placement of  the
 latex membrane.  Long-term flexible-wall! tests with heptane have been carried
 out successfully with this method.

      Materials compatibility has also been a problem in  fixed-wall tests with
 corrosive test fluids.  Stainless steel  permeameters and pressure fittings
 were damaged in tests with chronic acid  (Monserrate, 1982).  Several
 researchers have used plexiglass devices with  Teflon® fittings  to avoid such
 problems.

 4.3.4  Effect  of Backpressure

      Slight deviations from full  saturation have been  shown  to  significantly
 affect measured permeability values  (Mitchell  et al.,  1965).   Recognizing
 this,  some researchers include in the test method a  saturation  step involving
 backpressurlng.   Zimmie  et al. (1981)  noted that many  permeability determina-
 tions  are made using  backpressure to promote complete  saturation and  then
 releasing or lowering the  backpressure during  the permeability  test.  When
 this  1s done,  dissolved  gases  immediately  begin  to  come  out  of  solution,
 causing the  measured  permeability values to decrease.  Zimmie et al»  (1981)
 concluded,  "The maximum, fully saturated permeability  value  should be deter-
mined.  It is  necessary  to  utilize backpressure  to properly  saturate the
 specimen  whether  or not  the  actual permeability  test utilizes backpressure."

4.3.5  Effect  of  Hydraulic Gradient

     Mitchell, Hooper, and Campanela  (1965), in  tests*with a silty clay,
found evidence that rapid  infiltration of water  could cause migration of fine
particles  that tended  to plug  conducting pore spaces and reduce flow rates.
Mitchell and Younger  (1967) measured permeability to water of a compacted
silty clay as a function of  hydraulic gradient.  A gradual increase  in the
gradient from 0 to 17  over 26 days resulted in a corresponding  increase
1n permeability from  less than 5 pvp 10~7 to 5.4 x 10~6 cm/s.  The  in-
crease was approximately linear in the region of gradients of about  4 to 10,
the curve of permeability versus hydraulic gradient tending to flatten at
the lower and higher gradients.  The nonlinear behavior at the higher gradi-
ents may have been the result of movement of fine soil particles. Other
researchers—Olsen (1965) and Hamilton (1979)—have reported data
                                    4-14

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that show no significant effect of hydraulic gradient on either discharge
velocity or permeability to water.,          ,

     Under a cooperative agreement with the U.S. Environmental Protection
Agency  (EPA), Daniel  (1982) investigated the effect of hydraulic gradient on
permeability.  Water, (actually 0.01 N calcium sulfate) as well as other
permeant fluids were  tested at gradients of 10, 50, 100, and 300 in flexible-
wall cells, fixed-wall permeameters, and consolidation cells.  The perme-
ability of kaolinite  to water did not vary with hydraulic gradient in any
test device.  Changes in hydraulic gradient caused a slight increase in
permeability for kaolinite permeated with methanol in flexible-wall cells.
In fixed-wall permeameters and consolidation cells, however, the trend was
for decreasing permeability with decreasing gradient in tests with methanol.
Due to  large variations in the test data obtained for fixed-wall permeam-
eters,  the results of the tests were somewhat inconclusive.

     In other research funded by the EPA, Brown, Thomas, and Green (1984)
studied the effects of hydraulic gradient on the permeability of three clay
soils to two organic wastes--a xylene waste and an acetone waste.  It was
concluded that hydraulic gradients of 31, 91, and 181 did not greatly affect
the permeabilities in either presaturated or unsaturated samples.

4.3.6  Criteria for Concluding a Test

     Clay-chemical compatibility tests should be continued until all  changes
in permeability resulting from the interaction of the chemical with the clay
have been observed.  To satisfy this condition, compatibility tests should be
concluded only if the slope of the permeability versus time curve does not
vary significantly from zero (steady-state permeability has been reached) and
at least one pore volume of fluid has passed through the clay.  If the first
condition is not met, there is no assurance that reactions of the chemical
with the clay are complete.  If the second condition is not met, there is no
assurance that the permeant has contacted all  of the clay in the column.  In
order to satisfy the above conditions, it is necessary to determine the
chemistry of both the influent and effluent (to detect breakthrough)  and
report pore volumes through samples as well as real  time.  (Conclusion from a
workshop on Permeability Testing, Atlanta, GA, January 1984, unpublished.)
                                                    *
     A statistical  procedure was developed at Duke University (Monserrate,
1982;  Peirce and Witter,  1986)  to determine when a test should be concluded,,
Readings of column level  and time are taken at certain intervals throughout
the test.  The hydraulic conductivity is computed for  each time interval.
From this set of data the first 10 points are taken  and a linear regression
analysis is performed to determine the slope of the  hydraulic conductivity
vs. time curve.   The first point is then dropped and another value is added
on the other end.  The slope is calculated again, and  so on.  In the
beginning of the test this slope will  be fairly large, but as the test
progresses it will  decrease and approach zero when steady-state is obtained,,

     The criteria for when steady-state is obtained  will  be taken when two
criteria are met--
                                    4-15

-------
      t  When the slope at the curve does  not  vary  significantly from zero
         at the 95-percent confidence level, and

      t  At least one pore-volume  of the liquid is  passed through the sample
         (Peirce, 1984).

 4.4  SUMMARY OF AVAILABLE RESEARCH  DATA

      Numerous studies pertaining  to the effects of chemicals on clay soil
 permeabilities have  been  carried  out by researchers at universities and by
 private  firms across the  country  during the last few decades.  Research has
 been  sponsored by the EPA,  the Army Corps of  Engineers, the Chemical
 Manufacturers Association,  and others.  Among the  classes of compounds that:
 have  been  tested are aliphatic hydrocarbons,  chlorinated aliphatics, aromatic
 hydrocarbons,  alcohols, glycols,  ketones, carboxylic acids, amines, and
 aromatic nitro compounds.   In addition to tests with single-compound test
 solutions, many studies have  been carried out using complex chemical mix-
 tures.   In tests involving  actual wastes or leachates (obtained by passing
 water through wastes),  the  exact  composition  of the fluid is usually not
 known although major components and important parameters are usually identi-
 fied  and quantified.

      The results of  some  of the most significant permeability tests involving
 specific organic solvents are presented in Table 4-1.  The results of
 permeability tests involving wastes are presented  in Table 4-2.

      Some of the studies  summarized here and  in more detail in Section 4.5
 have  shown that certain pure, concentrated organics can drastically alter the
 permeability of clay soils  under  the conditions of the laboratory test.
 These test results have led to widespread concern  over the possible seepage
 of wastes into the environment from clay-lined disposal  facilities.  It
 should be emphasized that clay liners in disposal  facilities are most often
 in  contact with leachate  having much  lower organic solvent concentrations
 than  the test  solutions associated  with the drastic permeability increases
 seen  in  some laboratory studies.  Laboratory studies performed with less
 concentrated test solutions (either actual wastes or leachates or dilutions
 prepared in  the laboratory) do not  appear to produce such effects.

      Because of the  wide variations  in the soils used* in clay liners and the
 leachates to which they will be exposed during service,  testing of the actual
 Uner/leachate  system is necessary  to confirm compability.

4.5   PERMEABILITY STUDIES TO INVESTIGATE CLAY-CHEMICAL INTERACTIONS

     The major  findings of various  research efforts to investigate effects on
permeability of  clay-chemical  interactions are presented in this section.

4.5.1  Observations  by Macey (1942)  on Effects of Organics  on Fireclay

     As a result of permeability experiments with fireclay,  Macey  (1942)
concluded that the rates of flow of benzene, nitrobenzene,  and pyridine
                                    4-16

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       TABLE  4-1.   RESULTS OF  PERMEABILITY TESTS WITH ORGANIC CHEMICALS

                                *  ^r '
 ALIPHATIC AND AROMATIC  HYDROCARBONS

 Heptane

 Fixed-wall permeameter  tests  at high gradient with four clays showed rapid
 permeability increases  and breakthrough.  The increase in permeability was
 more  than 3  orders of magnitude in an illite clay.  Baseline permeabilities
 were  established  in  the same  sample with 0.01 N calcium sulfate prior to
 introducing  the test solution.  (Anderson, 1981)

 Benzene

 The flow rate of  benzene through fireclay was of an enormously higher order
 of magnitude than  the flow rate for water.  (Macey, 1942)

 In a  column  test  under  a head of 701 cm (23 feet), signs of full penetration
 throughout the clay  material were observed after 36 days; in a similar column
 with  water as the  permeant fluid the liquid level dropped less than 2.54 cm
 (1 inch) over a 100-day period.  Samples were 91 cm in height and 2.54 cm in
 diameter.  (White, 1976, unpublished data)

 Following an initial decrease in permeability (compared to permeability to
 deionized water established in a similar sample), total breakthrough occurred
 on the eighth day  of testing when Ranger shale was exposed to benzene in a
 fixed-wall permeameter  under low hydraulic gradient.  (Green et al., 1979)

 Benzene did  not penetrate compacted Ca-montmorillonite that was first
 saturated with 0.01  N calcium sulfate even at hydraulic gradients as high at
 150.   (Olivieri,  1984)

 In flexible-wall tests with a Georgia kaolinite, permeability decreased until
 the tests were terminated.  The final value was approximately 2 orders of
magnitude lower than the initial permeability.  (Acar et al., 1984a)

Xylene
                                                    *

Following an initial  decrease in permeability, total  breakthrough occurred on
the 25th day of testing when fireclay was tested in a fixed-wall  permeameter
under low hydraulic gradient.  In  Ranger shale,  a slight decrease in perme-
ability was observed and remained  steady until  the test was terminated at 40
days.  In Kosse kaoline, a slight  decrease in permeability was followed by an
increase to about the initial  level, which persisted until  the test was
terminated at day 36; changes did  not exceed half an order of magnitude.
 (Green et al.,  1979)

In column tests under very low gradient, intrinsic permeabilities were higher
than permeability to water by at least 1 order of magnitude in samples of
Lake Bottom,  Nicholson,  Fanno, Chalmers, and Canelo clays.   Permeabilities

                                        ~~(continued!
                                    4-17

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                            TABLE 4.1  (continued)
 Xylene  (con.)

 were  slightly  higher  than  for water  in three other soils.  The samples (5.8
 cm  in diameter and  5  cm  in height) were presaturated with xylene.  (Schramm,
 1981)

 Fixed-wall  tests  at high gradient with four clays showed permeability in-
 creases and breakthrough followed by nearly constant permeabilities roughly
 2 orders  of magnitude higher than baseline permeabilities.  Baseline perme-
 abilities were established in the same sample with 0.01 N calcium sulfate
 prior to  introducing  the test solution.   (Anderson, 1981)

 In  fixed-wall  permeameter  tests at-high gradient, the permeability of an
 unsaturated micaceous soil  was 4 orders of magnitude higher when exposed to
 xylene than when  tested with 0.01 N calcium sulfate.  (Brown et al., 1984)

 Xylene/Acetone                          ;

 In  fixed-wall  permeameter  tests at high gradient, the permeability of an
 unsaturated micaceous soil  to either pure acetone or pure xylene was greater
 than  the  permeability determined for mixtures of the two solvents.  The
 permeability of a mixture  of 87.5 percent xylene and 12.5 percent acetone
 was lower by 3 orders of magnitude than the permeability measured with pure
 xylene (though still  higher than the permeability to 0.01 N calcium sul-
 fate).  When the  acetone component was increased to 75 percent, the perme-
 ability was approximately  the same as that determined with pure acetone
 (i.e., about 1.5  orders of magnitude greater than the permeability to 0.01 N
 calcium sulfate).   (Brown  et al., 1984)

 Kerosene  (a mixture of aliphatics and aromatics)

 In column tests under very  low gradient, intrinsic permeabilities were higher
 than permeability to  water  by approximately 1 order of magnitude in samples
 of Lake Bottom, Nicholson,  Fanno, Chalmers, and Canelo clays.  Permeabilities
were slightly  higher  than  for water in three other soils.  The samples (5.8
 cm in diameter and 5  cm in  height) were presaturated with kerosene.
 (Schramm, 1981)

 In fixed-wall  permeameter  tests at high gradient, the permeability of an
 unsaturated micaceous soil   increased by 3 to 4 orders of magnitude compared
 to the permeability determined with 0.01 N calcium sulfate.  (Brown et al.,
 1984)

Naphtha

The permeabilities of two clays (Na-saturated and Ca-saturated montmorillon-
 1te) to naphtha were greater by several  orders of magnitude than their
permeabilities to water.   (Buchanan, 1964)
                                                                  (continued)
                                    4-18

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                             TABLE 4-1 (continued)
 Soltrol C (a light hydrocarbon liquid)

 Intrinsic permeabilities for samples tested with  the light  hydrocarbon were
 significantly higher than the permeabilities measured in  similar  samples
 exposed to water,  (van Schaik,  1970)

 Diesel  Fuel

 Fixed-wall  permeameter tests at  high gradient with  an unsaturated micaceous
 illite  produced highly variable  data inconsistent with the  pattern of perme-
 ability changes seen with other  liquid  hydrocarbons.  Permeability was
 greater by 1 to 2 orders of magnitude than  the permeability measured with
 0.01  N  calcium sulfate in a similar sample.  (Brown et al., 1984)

 Paraffin Oil

 In fixed-wall  permeameter tests  at  high gradient  with an .unsaturated mica-
 ceous illite,  permeability was greater  by about 1 order of  magnitude than
 the permeability measured with 0.01 N calcium sulfate in a  similar sample.
 Maximum values were  obtained after  the  passage of one pore  volume.  (Brown et
 al.,  1984)

 Gasoline

 In fixed-wall  permeameter tests  at  high gradient  with an unsaturated mica-
 ceous illite,  permeability was greater  by 1 to 2  orders of magnitude than
 the permeability measured with 0.01 N calcium sulfate in a  similar sample.
 (Brown  et al.,  1984)

 Motor Oil

 In fixed-wall  permeameter tests  at  high  gradient  with  an unsaturated mica-
 ceous illite,  permeability increased by  about  1 to  2  orders of magnitude as
 2.5 pore  volumes  of  fluid were passed through  the sample.   (Brown et al.,
 1984)                                                „

 ETHERS

 Dioxane

 Kaolinite initially packed and permeated with water was permeated with
 anhydrous dioxane until complete displacement of the water was achieved.
 Replacement  of water by dioxane was accompanied by about a 20- to 30-percent
 increase  in  intrinsic permeability.  This permeability was much lower,
 however, than the values determined for kaolinite  beds initially prepared
with dioxane.  (Michaels and Lin, 1954)

                                                                  (continued)'
                                    4-19

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                            TABLE 4-1 (continued)
KETONES
                                         i
Acetone                                  ;

In fixed-wall permeameter tests under low hydraulic gradient, three clays
showed slight decreases 1n permeability  (compared to permeability to
delonlzed water established in a similar sample).  All tests were concluded
before 40 days.  Less than 0.5 pore volumes were passed through the sample,,
(Green et al., 1979)                     ;

Fixed-wall permeability tests at high gradient with four clays showed initial
permeability decreases followed by increases compared to baseline.  Baseline
permeabilities were established in-the same sample with 0.01 N calcium sul-
fate prior to introducing the test solution.  Extensive shrinking and crack-
Ing in the soils were observed after permeation.  (Anderson, 1981)

In flexible-wall tests with a Georgia kaolinite, an immediate decrease in
permeability was followed by an increase, the final value stabilizing at
approximately double the initial permeability (Acar et al., 1984)

Acetone  (high and low concentration)

An Increase over baseline permeability (established with 0.01 N calcium sul-
fate in  similar samples) was seen in an unsaturated micaceous soil for solu-
tions where the acetone concentration was 75 or 100 percent.  Samples tested
with lower concentrations of acetone did not show appreciable changes in
permeability compared to the 0.01 N calcium sulfate.  Tests were carried out
1n fixed-wall permeameters at high gradient.  (Brown et al., 1984)

Acetone  (low concentration)

Permeability decreased slightly 1n a Georgia kaolinite clay tested 1n a
flexible-wall permeameter with a solution containing a low concentration of
acetone  (I.e., below 0.1 percent) prepared in 0.01 N calcium sulfate.  (Acsir
et al.,  1984a)

ALCOHOLS, GLYCOLS, PHENOL

Methanol

Permeability decreased slightly (compared to permeability to deionlzed water
established in a similar sample) when Ranger shale was exposed to methanol
under low hydraulic gradient in a fixed-wall permeameter.  The test was
terminated after 30 days.  (Green et al., 1979)

Fixed-wall permeameter tests at high gradient with four clays showed steady
permeability increases compared to baseline.  Baseline permeabilities were
established in the same sample with 0.01 N calcium sulfate prior to introduc-
ing the test solution.  Examination of the methanol-treated samples revealed
development of large pores and cracks.  (Anderson, 1981)

                                                                  (continued)

                                    4-20

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                            TABLE 4-1 (continued)
Methanol  (con.)

Test  results with Lufkin clay in flexible-wall cells showed essentially no
change  in permeability with time when samples were permeated with methanol.
The permeability to methanol was virtually the same as with 0.01 N calcium
sulfate.  (Daniel, 1983)

At high hydraulic gradients, kaolinite was found to have a higher conduc-
tivity  to methanol than to water regardless of the permeameter types; fixed-
wall, flexible-wall, and consolidation permeameters were used.  In the
flexible-wall and consolidation permeameters, kaolinite is about twice as
permeable to methanol as to water.  (Foreman and Daniel, 1984)

Isopropyl Alcohol

In column tests under very low gradient, intrinsic permeabilities were higher
than  permeability to water by almost 1 order of magnitude in samples of
Nicholson, Fanno, and Canelo clays.  Permeability values were the same or
slightly higher than baseline in five other soils.  The samples (5.8 cm in
diameter and 5 cm in height) were presaturated with the alcohol.  (Schramm,
1981)

Glycerol

Permeability decreased slightly (compared to permeability to deionized water
established in a similar sample) when Ranger shale was exposed under low
hydraulic gradient to glycerol  in a fixed-wall permeameter.  The test was
terminated after 36 days.  (Green et al., 1979)

Ethylene Glycol

Fixed-wall permeameter tests at high gradient showed permeability decreases
compared to baseline followed by increases in three clays;  a smectitic clay
showed an initial rapid increase followed by a slower but continuous increase
in permeability.  Baseline permeabilities were established in the same sample
with  0.01 N calcium sulfate prior to introducing the test solution (Anderson,
1981)

In column tests under very low gradient, intrinsic permeabilities were an
order of magnitude lower than permeabilities to water in Chalmers clay,
Mohave clay, and River Bottom sand.  Values were slightly lower in Lake
Bottom, Nicholson, Canelo, and Anthony clays and slightly higher in Fanno
clay.  The samples (5.8 cm in diameter and 5 cm in height) were presaturated
with  the ethylene glycol.  (Schramm, 1981)

                                                                  (continuedj
                                    4-21

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                             TABLE 4-1 (continued)
 Phenol  (949 mg/L)

 In column tests with a lacustrine clay (packed to  discharge  2 ml/day),  no
 significant effect on permeability was noted when  deionized  water was
 replaced by the phenol solution as the permeant fluid.   (Sanks and Gloyna,
 •Ly / / j

 Phenol  (low concentration)

 Permeability decreased slightly in a Georgia kaolinite  clay  tested in a
 flexible-wall  permeameter with a solution  containing a  low concentration of
 phenol  (I.e.,  below 0.1 percent) prepared  in 0.01  N calcium  sulfate.  (Acar
 et al.,  1984a)                     .

 Phenol  (high concentration)

 In flexible-wall  tests with  a  Georgia kaolinite and a high-strength phenol
 solution,  an immediate decrease in permeability was followed by an increase,
 the final  value stabilizing  at approximately double the  initial perme-
 ability.   (Acar et al., 1984a)

 AMINES

 Aniline

 Fixed-wall  permeability tests  at high gradient  with four clays showed perme-
 ability  increases and breakthrough.   Baseline permeabilities were established
 in the same sample with 0.01 N  calcium sulfate  prior to  introducing the test
 solution.   Extensive  structural  changes  in the  upper half of the soil columns
 were observed following permeation with  aniline.   The aggregated structure
 was characterized by  visible pores and cracks on the surface of the soils.
 (Anderson,  1981)

 Pyridine
                                                     «
 The flow rate of  pyridine through  fireclay was  of  an enormously higher order
 of magnitude than  the rate of flow for water.   (Macey, 1942)

 CHLORINATED ALIPHATICS

 Carbon Tetrachloride

 Permeability decreases  slightly  (compared to permeability to deionized water
 established in a similar sample) when Ranger shale was tested under low
 hydraulic gradient  in a fixed-wall permeameter.  The test was terminated
after 14 days.  (Green  et al., 1979)

                                                                  (continued)
                                    4-22

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                            TABLE 4-1  (continued)
Trlchloroethylene

Permeability decreased slightly  (compared to permeability to deionized water
established in a similar sample) when fireclay was tested under low hydraulic
gradient  in a fixed-wall permeameter.  The test was terminated after 36 days.
(Green et al.f 1979)

OTHER

Acetic Acid

Tests at high gradient in fixed-wall permeameters showed continuous perme-
ability decreases to baseline in two clays.  Tests with smectitic and ill He
clays showed permeability increases after initial decreases.  Baseline
permeabilities were established  in the same sample with 0.01 N calcium
sulfate prior to introducing the test solution.  The permeability decreases
were attributed to partial soil dissolution and migration of particles, which
temporarily clogged the fluid conducting pores.  Progressive soil piping
eventually caused the increase in permeability.  (Anderson, 1981)

Nitrobenzene

The flow rate of nitrobenzene through fireclay was of an enormously higher
order of magnitude than the flow rate for water.  (Macey, 1942)

In flexible-wall  tests with a Georgia kaolinite, permeability decreased until
the tests were terminated.  The final value was approximately 2 orders of
magnitude lower than the initial  permeability (Acar et al., 1984a)
                                    4-23

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             TABLE 4-2.   RESULTS  OF  PERMEABILITY TESTS WITH WASTES
 "Xylene  Waste"  (paint  solvent  containing xylene with 25 percent paint pig-
 ments  and  trace amounts  of water)

 In  fixed-wall permeameter tests, the permeability of three clay soils, pre--
 saturated  with  0.01  N  calcium  sulfate,  increased rapidly upon exposure to
 xylene waste after the cumulative  flow  exceeded 0.2 to 0.4 pore volume.
 Permeabilities  were  2  to 4 orders  of magnitude greater than permeabilities
 measured with 0.01 N calcium sulfate.   Highest permeabilities measured on
 Initially  unsaturated  samples  were greater by 1 to 2 orders of magnitude than
 for samples that were  initially saturated with the calcium sulfate.  (Brown
 et  al.,  1983)

 "Acetone Waste"  (a chemical manufacturing waste containing 91.7 percent
 acetone, 4 percent benzene, and 0.6 percent phenol)

 In  fixed-wall permeameter tests, the permeability of three clay soils, pre-
 saturated  with  0.01  N  calcium  sulfate,  initially decreased (minimum perme-
 ability  at approximately 0.5 pore  volume) and then steadily increased.
 Permeabilities were  2  to 4 orders  of magnitude greater than permeabilities
 measured with 0.01 N calcium sulfate.   Highest permeabilities measured on
 initially  unsaturated  samples  were greater by 1 to 2 orders of magnitude than
 for samples that were  initially saturated with the calcium sulfate.  (Brown
 et  al.,  1983)

 Perchloroethylene Waste

 There  is evidence that a perchloroethylene waste, which formed a separate,
 denser than water phase, contributed to the failure of a clay liner at a
 surface  impoundment.   (Personal communication, 1984)

 "Acid  Prowl" (pesticide  wash of very low pH; higher viscosity than water)

After  several days of exposure to a lacustrine clay packed in a fixed-wall
 column, the water reacted with the soil  to produce chlorine gas.  Over a
 5-week period, the flow  of liquid from the column was, irregular due to
 clogging of pores by the gas.  (Everett, 1977)

 "Acid Wash" (42  percent  sulfuric acid with about 5 percent organics: higher
viscosity  than water)

Permeability of a lacustrine clay packed in shrink tubing increased by about
1 order of magnitude over a period of 19 ;days.  The permeability was lower,
however,  than values obtained when the soil  sample was exposed to water.
 (Everett,  1977)

                                         ~(continued!
                                    4-24

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                            TABLE 4-2 (continued)
"Mother Liquor"  fan acid wash with pH of 0.37; higher viscosity than water)

Permeability of a lacustrine clay packed in shrink tubing was lower than the
value obtained when the soil sample was exposed to water.  The waste may have
reacted with the soil, liberating gases and increasing pore pressures and
clogging flow.   (Everett, 1977)

"Hydrazo Benzene" (33 percent methanol, 12.8 percent sodium hydroxide, 15.5
percent sodium formate, and 1.5 percent hydroazobenzene and azobenzene; more
viscous than water)

Permeability of a lacustrine clay packed in shrink tubing was slightly lower
than the value obtained when the soil sample was exposed to water.  Tests
were carried out for 34 days under low gradient (less than 100 cm).
(Everett, 1977)

"Acid Waste" (100 mM HC1/L)

Due to reaction with carbonates, much higher permeabilities were observed in
tests with lacustrine clay compared to permeabilities determined with
deionized water.  (Sanks and Gloyna, 1977)

"Basic Waste" (100 mM NaOH/L)

Permeabilities in a lacustrine clay decreased compared to the values measured
with deionized water.  (Sanks and Gloyna, 1977)
                                    4-25

-------
 through  clay are "of an  enormously  higher  order  than for water."  Analytical
 reagent-grade_organics were  used.   All  the organic  liquids passed through the
 clay at  flow rates  100,000 to  1,000,000 times greater than the flow rate of
 water through the same clay.   The high  rates of  flow produced experimental
 difficulties because of  the  high  resistance to flow of the testing apparatus,
 and  the  experiments were finally abandoned. Differences between the viscosi-
 ties of  the  organic fluids and of water are not  sufficient to account for the
 very large permeability  changes that were  observed.

 4.5.2 Tests With Kaolinite  and Organic Solvents by Michaels and Lin (1954)

      Michaels and Lin (1954) measured the  permeability of high-purity
 kaolinite to nitrogen gas, cyclohexane,  acetone, dioxane, methanol, and
 distilled water.  Tests  were also conducted to determine the effect of
 replacement  of one  permeant  liquid  by another.   The investigation was one
 part of  a broad program  of fundamental  research  sponsored by the U.S. Army
 Corps of Engineers  and by industrial contributions  and was carried out at the
 Massachusetts Institute  of Technology (MIT) Soil Stabilization Laboratory.

 4.5.2.1  Test Method--
      Permeability tests  were conducted  in  a 5.1-cm  (2-inch) -diameter fixed-
 wall  permeameter  cell.   Bed  thickness was  1.1 to 1.8 cm.  The base-exchange
 capacity of  the kaolinite was  determined to be 5.0 + 0.5 meq/100 g.
 Samples  were dried  for 24 hours at  160°C prior to saturation by the
 organic  liquids for the  permeability test.

      Prior to permeability testing, each sample was submerged in the fluid to
 be tested (either organic liquid or water).  The wetted samples containing
 known amounts of  clay were poured into  the  permeability cell, entrapped air
was  removed,  and  the  sample was consolidated by means of a confining piston.
Samples  were consolidated to several void  ratios (volume of voids/volume of
solid) for each test  fluid.  Void space  was determined through column bulk
density  and  the true  density of kaolinite.

      For the  permeability tests, a hydrostatic head not exceeding 10 percent
of the compaction pressure was maintained.  Permeabilities were determined
for each void  ratio.. Permeability coefficients determined for separate clay
samples  prepared with a given  fluid and  compacted to essentially the same
void  ratio were found to  be reproducible to within 10-percent.

     The effect of  change of fluid medium on the permeability of a confined
clay was determined through a  series of  desolvation experiments.  Kaolinite
initially packed and permeated with water was subsequently permeated with
dioxane  until the water was completely displaced (as evidenced by constant
permeability  to dioxane).  The dioxane was then displaced with acetone  under
similar  conditions.   Finally, warm,  dry  nitrogen was passed through  the
sample until  the bed was  solvent-free.  Beds initially tested with the
organic  liquids (methanol, dioxane,  acetone, and cyclohexane) were similarly
treated with dry nitrogen until all  solvent was removed.
                                    4-26

-------
     The permeability to nitrogen of the desolvated samples was then
determined and compared to the permeability with the original  permeant
fluid.                            J          -

4.5.2.2  Test Results—
     The intrinsic permeabilities (cm2) of samples packed at different
void ratios, measured for organic solvents and for nitrogen, are shown in
Figure 4-3.  Predictably, the permeabilities increased with increasing void
ratio.  The data also indicate that permeability at any given void ratio
decreases with increasing polarity of the permeant.

     As a result of the desolvation experiments, the authors concluded that:

     Whatever specific effects these permeant  liquids exert on the kaolin-
     ite persist when the clay is thoroughly dried in the confined state.
     The reduced permeabilities of kaolinite to these liquids relative to the
     values observed for this clay to gas when packed in the dry state
     apparently cannot be ascribed to adsorbed liquid films, abnormally high
     liquid viscosities, or electro-osmotic effects. ...  It seems most
     probable, therefore, that the lower permeabilities of kaolinite to these
     liquids than to nitrogen are caused by improved dispersion, and possibly
     more orderly packing of the solids in more polar media.

     Results of the desolvation experiments show the effect of replacement of
permeant fluid on the permeability of the kaolinite.  For samples sedimentecl
from and initially permeated with methanol, dioxane, acetone,  or cyclohexane
and then exhaustively permeated with warm, dry, nitrogen gas,  the final gas
permeability is found to be equal, within the  limits of experimental accu-
racy, to the permeability to the initial permeant liquid at the corresponding
void ratio.  This is particularly true at low  void ratios.  An increase in
permeability upon drying is observed if the initial void ratio is high.

     Specific observations by Michaels and Lin include the following:

     o  Replacement of water by dioxane is, in all cases, accompanied
        by about a 20- to 30-percent increase  in permeability; the dioxane
        permeabilities through these beds are, however, much lower than the
        values determined for kaolinite beds prepared^ initially in dioxane.

     o  Replacement of the dioxane with acetone leads to a small  additional
        permeability increase approximately when water is the  initial
        permeant fluid.

     o  Displacement and evaporation of the acetone with dry nitrogen  is
        accompanied by a great increase in permeability; the magnitude of
        this increase is greatest for kaolinite samples confined initially at
        high void ratios.
                                    4-27

-------
                                               Permeants
                                            x - Water
                                            0 - N2
                                            a - Cyclohexane
                                            A - Acetone
                                            A - Oioxane
                                            + - Methanol
                                                                    2.4
Source: Michaels and Lin, 1954
            Figure 4-3. Intrinsic permeabilities as a function of void space (e)
                           measured for different permeants.
                           4-28

-------
 4.5.2.3  Discussion—
      Intrinsic permeabilities reported by Michaels  and  Lin  cannot  be directly
 compared with permeability data from other tests  because  the measurement pro-
 cedure is unique..  No information is provided  about the amount  of  fluid passed
 through the sample in determining each of the  reported  permeabilities.

      While samples used in permeability tests  are usually air-dried, the
 clay samples used by Michaels and Lin were dried  for 24 hours at 160°C, a
 condition that could cause irreversible changes  in  clays  and organic matter.
 It is possible that the adsorptlve properties  of  the kaolinite  were
 permanently altered by this drying procedure.  The  kaolinite mineral,
 halloysite, will  not rehydrate if the interlayer  water  is removed.

 4.5.3  Study by Buchanan (1964)  of the Effect  of  Naphtha  on Montmorilignite

      Buchanan (1964) at Texas A&M University studied permeabilities of sodium-
 and calcium-saturated montmorillonite when these  clays  were permeated by water
 and naphtha.  Permeabilities of the two clays  to  naphtha  were greater by
 several orders of magnitude than their permeabilities to  water, even with
 reductions in void ratios for the samples treated with  naphtha.  The data also
 suggest that the permeability of the sodium-saturated clay  is more
 dramatically affected by the naphtha.  Permeability differences were thought
 to be at least partially due to the inability  of  naphtha  to form an
•immobilized liquid film on the clay mineral surfaces.  Buchanan's  data are
 summarized in Table 4-3.

 4.5.4  Study by Reeve and Tamaddoni  (1965) of  the Effect  of Electrolyte
        Concentration on Permeability of a Sodic Soil

      Reeve and Tamaddoni (1965)  of the U.S. Department  of Agriculture studied
 the effects of high-salt, high-sodium solutions on  the  permeability of a
 highly sodic soil.  California Waukena clay loam  containing about  15 percent
 of expanding lattice-type clay was tested in the  laboratory and in the field.

 4.5.4.1  Test Method-
      Solutions of varying concentrations but with constant  sodium  adsorption
 ratio (SAR) were used in the tests.   Test solutions were  prepared  from sodium
 chloride (NaCl)  and calcium chloride (CaCl2) at SAR levels  of 0 (100
 percent CaCl2),  80 (a partially reclaiming solution),-180 (the  equilibrium
 solution of the  natural  soil), and <» (100 percent NaCl).  For each SAR level,
 seven ionic concentrations (63,  125,  250,  500, 1,000, 2,000, and 4,000
 meq/L)  were tested in a selected sequence. Laboratory  tests were  carried out
 in fixed-wall  5.4-cm (2.125-inch)  ID cylinders.

 4.5.4.2  Test Results—
      The test results indicate that  permeability  is a function  of both the
 absolute concentration and the SAR of the  initial solution.  Permeability
 increased with increasing SAR value  and ionic  concentration •  The
 permeability-concentration relationship was found to  depend markedly on the
 initial  solution  concentration (i.e.,  if the initial  solution concentration
                                    4-29

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  TABLE 4-3.  VOID RATIO AND COEFFICIENT OF PERMEABILITY RELATIONSHIPS
         -FOR CALCIUM- AND SODIUM-MONTMORILLONITE PERMEATED BY
                           WATER AND NAPHTHA3
Clay
Calcium-saturated
smectite
Sodium-saturated
smectite

Void
ratio
1.72
3.75
Water
Permeability
(cm/s)
1.6 x 10-9
5.2 x 10-11

Void
ratio
1.52
1.31
Naphtha
Permeability
(cm/s)
6.4 x 10-5
3.8 x 10-5
aData from Buchanan (1964).
   TABLE 4-4.  SUMMARY OF SOIL PERMEABILITY WITH SOLTROL C AND WATER3
          Soil
 (bulk density in g/cm
     pi
i3)   W,
    Intrinsic
ermeabllity (urn2)   Permeability. K (cm/s)
'ater
Oil
Water
Oil
 Cavendish loamy sand      4.94
 (bulk density:
 1.44 g/cm3;
 6 percent clay)

 Chin sandy clay loam      0.73
 (bulk density:
 1.25 g/cm3;
 18 percent clay)

 Chin sandy clay loam      0.22
 (bulk density:
 1.38 g/cm3;
 18 percent clay)

 Lethbridge clay loam      0.51
 (bulk density:
 1.22 g/cm3;
 37 percent clay)
                   9.38   4.8 x lO'3   3.0 x 10~3
                   5.45   7.1 x lO-4   5.1 x 10~3
                   2.53   2.1 x 10~4   1.4 x 10'3
                   6.10   5.0 x 10-4   3.3 x lO"3
aData from van Schaik  (1970).
                               4-30

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 was low,  the range of permeability values  with  varying  solution  concentra-
 tions was lower than if the initial  solution  concentration was high, and
 vice versa.)  Apparently the degree  of flocculation  or  dispersion  that
 occurred  with the application of the initial  solution influenced the magni-
 tude of the permeability.

      In some of the tests a large change in solution concentration  (e.g.,
 from 125  to 1,000 meq/L)  was accompanied by a large  increase  in  outflow due
 to  sidewall  leakage as a consequence of the contraction of the previously
 swollen mass.

      In the test series in which initially low  concentrations (63 meq/L)
 were increased stepwise to 4,000 meq/L and then reduced to the initial con-
 centration,  reproducibility of permeability values as a function of concen-
 tration was good.  These results suggested that a reversible  swelling
 process was occurring.  In the test  series in which  initial concentrations
 of  1,000  meq/L were increased to 4,000 meq/L  and then reduced to 63 meq/L,
 results showed a gradual  decrease in permeability with  a given solution
 concentration.  This was  attributed  to slaking  or particle rearrangement
 that led  to permeability decreases that progressed with time.

      The  permeability of the Waukena soil  to  a  saturated calcium sulfate
 (CaS04) solution was an order of magnitude lower than the lowest values
 measured  with the test solutions.

      Test results showed  that intake rates measured in  the field at high
 electrolyte  concentrations were  approximately three times as great as
 corresponding permeabilities measured  in the  laboratory.  However, the
 fractional  change was  essentially the  same at equal electrolyte  concentra-
 tions.

 4.5.5   Tests  by van  Schaik and Laliberte (1968)  of Permeability  of Soils
        to a  Liquid Hydrocarbon

      Permeability data  are reported  by  van Schaik (1970) for three soils
 tested with  tap water  and  with a  light  hydrocarbon liquid (trade name
 Soltrol C).   Permeability  measurements were made on samples that had been
 vacuum-saturated.  The  intrinsic  permeabilities with .the oil  were first
 reported  by  van  Schaik  and  Laliberte  (1968).

 4.5.5.1   Test  Results—
     The  saturated  intrinsic  permeability of  the three  samples varied between
 0.22 and 4.94 isnf-  for water.  For oil, the values ranged between 2.53 and
 9.38 urn*.   The  data are summarized in Table 4-4.

4.5.5.2  Discussion—
     The test apparatus used  in the study was  designed to measure properties
of unsaturated porous media.  The number of pore volumes displaced by the
test fluid during the permeability determination was not reported.   Details
of the test procedure used also were not given in the references  cited.   In
spite of these  limitations, the intrinsic permeabilities are  useful  for
                                    4-31

-------
 comparing  the  relative  permeabilities of the various soils to water and oil.
 The  Increased-permeabilities of the  soils when exposed to the oil are con-
 sistent with the  later  findings by Anderson (1981).

 4.5.6  Study by Everett (1977) of Permeability of Lacustrine Clay to Four
       Liquid  Wastes-

     Everett (1977)  investigated the permeability of lacustrine clays from
 Bay  County, Michigan, to four  liquid v/astes.  The purpose of the study was to
 establish  the  feasibility of a hazardous waste landfill in Bay County.  Three
 types of permeability test devices were used.  The results of the comparative
 tests with water  show no significant differences in the permeabilities
 measured in the different devices.

     The predominant mineral in the  soil ;was quartz, estimated to be 40 to 50
 percent.   Clay minerals present were illite and chlorite, each at about 10 to
 15 percent.  Other important constituents were dolomite (20 to 25 percent)
 and  calcite (10 to 15 percent).  The clay fraction was reported to average
 18.1 percent.  The mean cation exchange capacity of the soil (determined with
 ammonium acetate  solution) was low.

     Wastes used  in  the compatibility tests were "Acid Prowl," "Acid Wash,"
 "Mother Liquor,"  and "Hydrazo Benzene."  "Acid Prowl" is a pesticide wash of
 very low pH.   The "Acid Wash" was about 42 percent sulfuric acid 1n water and
 also contained about 5  percent organics including dichlorobenzidine,
 orthochloroaniline, and tars.  The waste labeled "Hydrazo Benzene" actually
 contained  about 1.5 percent hydroazobenzene and azobenzene.  Other components
 were methanol  (33 percent), sodium hydroxide (12.8 percent), sodium formate
 (15.5 percent), and water (36.7 percent).  The waste has a pH of 12.10.  The
 "Mother Liquor" was an  acid wash (pH of 0.37) of unknown use.  All waste
 samples were more viscous than water.

 4.5.6.1  Test  Method-
     Permeability to water was measured i:n three different test devices--
 commercial Soil Test® units (fixed-wall, 10.2-cm [4-inch] diameter, 10.2-cm
 [4-inch] sample height), PVC pipe (10.3-cm [4-inch] diameter, 15.2-cm
 [6-1nch] sample height), and shrink tubing (10-2-cm [4-inch] diameter,
 15.2-cm [6-1nch]  length).  Samples tested in the SoiLTest units and the
 shrink tubing were prepared in a standard Proctor mold according to ASTM
 specifications for modified Proctor compaction (D-1557-70).  The objective of
 preparing  the  samples was to obtain uniform packing.  The PVC pipe was packed
 1n a different manner,  not specified.

     Samples were saturated by backwashing with water for more than 2 weeks
 before permeability data were recorded.  Readings were taken over a 2-month
 period to  determine the permeability of the samples to water.  After testing
with water, three shrink tube columns and the PVC pipe columns were tested
with wastes.  Samples were allowed to saturate by backwashing with the waste
 until the  effluent showed the presence (by color or pH) of the waste.
                                    4-32

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     The tests were all conducted 1n falling head setups with a head of less
than 100 cm  (39.37 inches).  The metal test units were not used for testing
the wastes because of the corrosive nature of the wastes.

4.5.6.2  Test Results—
     "Acid Prowl" was tested in the PVC column.  After several days of con-
tact with the soil, .chlorine gas became noticeable at the outlet pipe.  After
2 weeks, the gas was no longer apparent, and liquid flow from the permeameter
ceased.  The column was allowed to stand with the waste fluid head for 3 more
weeks.  During this time the fluid reacted irregularly.  This behavior was
attributed to clogging of pores by chlorine gas generated with the sample.
Valid permeability readings could not be obtained.

     "Acid Wash," "Mother Liquor," and "Hydrazobenzene" were tested in shrink
tubes.  The permeabilities measured with the wastes were lower than the
corresponding permeabilities to water.  This may be due in part to the higher
viscosity of the wastes compared to water.  Values obtained after 19 days of
testing with "Acid Wash" showed a slight increase in permeability (about 1
order of magnitude) compared to the initial value.  For "Mother Liquor," test
data with the waste showed permeability to be lower by more than 2 orders of
magnitude than values measured with water.  These acid wastes may have
reacted with the soil-liberating gases, which would increase pore pressures
and consequently decrease the permeability.  In tests with hydrazobenzene,
permeability values were slightly lower than values obtained with water.
Permeability data are compared in Table 4-5.

4.5.6.3  Discussion—
     Although the compatibility tests were carried out for approximately 1
month, the volumes of liquid forced through the columns under the low gradi-
ents had to be very small.  The number of pore volumes displaced was not
specified.  Sufficient data were not presented to determine quantitatively
the effect attributable to the viscosity of the wastes.

4.5.7  Tests by Sanks and Gloyna (1977) of Permeability of Lacustrine
       Clay to Liquid Waste

     Sanks and Gloya (1977) tested five simulated liquid wastes with three
clays in column tests to determine effects on permeability.  The aqueous
waste solutions tested were chosen to be representative of materials that
might leak from containers of solid wastes.  The various substances contained
acid, base, and heavy metals.  Clays tested contained large percentages of
montmorillonite.  The columns were packed at densities low enough to dis-
charge 2 mL/day of distilled water at 152-cm (5-ft) head with an allowable
error of 10 percent.  After the tests with water, the columns were drained
and refilled with the waste fluid to be tested.

     Permeabilities with deionized water ranged from 4 x 1Q-8 to 1.2 x
10~7 cm/s.  Much higher permeabilities were observed when the acid waste
(100 mM HC1/L) was passed through the columns due to reaction with carbo-
nates.  Permeabilities decreased in tests with  the basic waste (100 mM
NaOH/L).  Phenol  at 10 mM/L (940 mg/L) appeared to have little effect on
permeability.
                                    4-33

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      TABLE 4-5.   PERMEABILITIES  MEASURED WITH  LACUSTRINE CLAY
                 EXPOSED  TO WATER AND  WASTE  LIQUIDS3
Day of
test data

1
3
5

15
19
29
32
34


3.4 x 10-10
1.3 x 10-9
1.5 x 10-9
With
"acid wash"
7.1 x 10-11
No flow
2.9 x 10-10
5.8 x 10-10
6.9 x 10-10
Permeability (cm/s)
With water
6.7 x 10-7
6.5 x 10-7
5.7 x 10-7
With
"mother liquor"
9.0 x 10-10
1.0 x 10-9
8.3 x 10-10
2.1 x 10-9
3.1 x 10-10


4.0 x 10-7
6.0 x 10-7
5.1 x 10-7
With
"hydrazobenzene"
9.0 x lO-8
7.8 x 10-8
No reading
1.3 x 10-7
1.3 x 10-7
aData from Everett (1977).
                              4-34

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      Heavy metals  tested,  HgCl2  at  30 mM/L  (8,100 mg/L) and ZnS04 x 7H20
 at 30 mM/L (8-,610  mg/L),  showed  no  effect except for one anomaly.

 4.5.8  Investigation  of the  Effect  of Organic Solvents on Clays by Green.
        Lee,  and  Jones (1979T	

      Under a grant from EPA's Kerr  Environmental Laboratory, Ada, Oklahoma,
 to the University  of  Texas at Dallas, Green, Lee, and Jones (1979) studied
 the impacts  of organic solvents  on  the shrink/swell behavior and permeability
 of four clay soil  materials—Ranger shale,  fire clay, Kosse kaoline, and
 Parker soil.  The  test results were compared to results with water.  The
 studies included extensive soil  characterization.  Soil properties are
 summarized in Table 4-6.  Organic solvents  tested were benzene, xylene,
 carbon tetrachloride, trichlorethylene, methanol, and glycol (Green et al.,
 1981,  1983).

 4.5.8.1  Test Methods--
      Swell properties of the clays  in contact with water, the organic
 solvents,  and various solvent mixtures v/ere investigated.  The swell
 properties were measured with a  6.4-cm-diameter consolidometer.  Care was
 taken  to prevent evaporation.  Clay core samples used in the tests were
 compacted  at optimum moisture content.  In  the consolidometer, samples were
 flooded with the test fluid and measurements of the swell or shrink behavior
 were made  as a function of time.

      Permeability  data were collected on 15 clay/solvent systems.  Test
 durations  ranged from 8 to 40 days.  Fixed-wall  permeameters us&d in the
 study  were thick-walled Pyrex glass, and all joints were Tefloi^-lined.  The
 test procedure was adapted from an ASTM method.   Samples were compacted at
 optimum moisture conforming to standard compaction procedures before transfer
 to  the  permeameters.  The test fluid was then introduced, the liquid level
 being  adjusted in  an 8-mm graduated standpipe.  Equilibrium permeabilities
 were estimated from curves of K(cm/s) versus time.  The number of pore
 volumes of permeant fluid passed through the samples was not reported.

 4.5.8.2  Test Results--
     Each  of the clay soils swelled to a greater extent when exposed to
 deionized water than with any of the pure solvents tested.  The shrink/swell
 behavior of the various clays in water and  in organic solvents is described
 in Table 4-7.  The final  percent swells for the  samples are,listed in Table
 H~O «

     Based on the  swelling data for both pure solvents and for mixtures, the
 authors concluded  that "in mixtures of solvents, a clay will  tend to  swell  as
 though it were immersed in the component of higher dielectric constant only"
 (Green et al., 1979).

     When Ranger shale was presented with benzene,  breakthrough occurred on
the eighth day of testing.  Breakthrough occurred  at about day 25 in  the fire
clay sample presented with xylene.
                                   4-35

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                  TABLE 4-6.   PROPERTIES OF SOILS TESTED*
Clays
Properties
Particle size distribution
(wt. %)
Clay
Silt
Sand
Total carbon (%)
Carbonate (%)
Cation exchange capacity
Atterberg limits
Plastic limit (moisture %)
Liquid limit (moisture %)
Optimum moisture content (%)
Corresponding dry density
(g/cm3)
Mineralogy (% of clay
fraction)
Kaolinite
Quartz
11 lite/mica
Chi ori te-montmori 11 oni te
Ranger
shale


40
59
1
0.60
0.32
54.4

36
46
17.5
1.73


24
28
24
10
Fire
clay


44
55
1.5
0.03
0
11.2

31
32
16
1.81


78
16
10
Negligible
Kosse
kaoline


53
47
0
0.12
0
13.4

38
50
31
1.36


85
10
5
Negligible
Parker
soil


10.5
70.5
19
3.18
0.42
14.1

22
26
18
1.86


14
Negligible
37
49
aData from Green et al., 1979.
                                   4-36

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        TABLE  4-7.  CLASSIFICATION OF CLAY-ORGANIC SOLVENT SYSTEMS
                     ACCORDING TO SWELL PROPERTIES3
Swelling Swelling then
only shrinking
RS/H20 RS/acetone
RS/glycerol KK/xylene
RS/methanol FC/acetone
RS/CC14 FC/TCE
RS/TCE FC/xylene (NS)
KK/water
KK/acetone
FC/water
RS = Ranger shale
FC = Fire clay
NS = Net shrinkage (net swell
observed unless indicated
otherwise)
Shrinking then
swelling
RS/benzene
KK/TCE
FC/benzene




Shrinking
only
RS/xylene (NS)
KK/CC14 (NS)
FC/CC14 (NS)

-


KK = Kosse kaoline
TCE = Trichloroethylene
Reproduced from Green,  Lee,  and Jones,  1979.
                               4-37

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             TABLE 4-8.  PERCENT SWELL FOR CLAY SOILS  IN  CONTACT
                       WITH ORGANIC LIQUIDS AND WATERa
Clay-soil
Ranger shale










Kosse kaoline


Fire clay



Solvent
Benzene
Benzene/acetone (3:l)c
Xylene
Carbon tetrachloride
Trichloroethylene
Acetone
Acetone/benzene (3:l)c
Acetone/water (l:l)d
Methanol
Glycerol
Water
Xyl ene
Acetone
Water
Xylene
Carbon tetrachloride
Acetone
Water
Percent swell"
0.05
5.75
-0.11
1.1
1.0
4.0
4.6
11.0
11.4
5.3
11.7
0.16
8.7
11.7
-0.25
-0.6
3.6
8.2
aAdapted from Green et al., 1979.
bNegative value indicates net shrinkage.
cMole percent.
dVolume percent.
                                    4-38

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      For  organic  solvents other than benzene, a decrease in permeability of
 Ranger  shale .was  observed for 5 to 10 days.  This decrease was followed by
 stable  readings at a minimum value.  The permeability coefficients reported
 are  shown  in Figure 4-4.  Although there is some scatter in the measurements
 characteristic of normal experimental error, the decreasing permeability
 trends  over the duration of the test period are evident.  The largest
 decrease  in permeability compared to water is seen with glycerol.  With
 carbon  tetrachloride, the decrease in permeability was followed by an
 increase  that continued to the end of the test period.

 4.5.8.3   Discussion--
      The authors  based their final conclusion, an empirical relationship for
 estimating the coefficient of permeability from dielectric constant of the
 permeant and packed bulk clay density, on what they judged to be final per-
 meabilities.  Their data do not indicate that stable permeabilities were
 reached, however, in all of the solvent clay systems tested.  Certainly the
 permeabilities measured just prior to breakthrough could not be classified as
 stable, yet these were used in obtaining the empirical equation to predict
 permeability.

 4.5.9  Anderson's Study (1981) of the Effects of Organics on Permeability

      Anderson (1981) at Texas A&M University studied seven organic fluids in
 comparative permeability tests.  Four native clay soils were tested—two with
 predominantly montmorillonite (smectitic) clay minerals but different chemi-
 cal properties, one with predominantly kaolinite minerals,  and one with
 predominantly illite.  Each soil  contained a minimum of 35  percent by
weight clay minerals and exhibited a baseline permeability  of less than
 1 x 10~7 cm/s when compacted at optimum water content.  Organic solvents
 tested were reagent grade ethylene glycol, acetone,  heptane, xylene (mixed
 isomers), aniline, glacial  acetic acid and methanol.  The control  fluid used
 to establish the baseline permeability for each soil was a  standard aqueous
 solution of calcium sulfate (0.01 N CaS04).  (Although it was not noted
 in the initial  publication of this research, the methanol used in the
 experiment contained 20 percent water [Anderson 1982].)

     Characteristics of the four soils used in the tests are presented in
Table 4-9.  The percentage of soil voids filled withjvater  at compaction at
 optimum moisture content was approximately 75 percent for the two smectitic
 clays and approximately 90 percent for the other two samples.  The minimum
 permeability for each sample occurred at or just above the  optimum moisture
 content (Anderson et al., 1981; Brown and Anderson,  1983).

 4.5.9.1  Test Method--
     Permeability was measured in constant head tests on soil cores compacted
at or above optimum water content.  Pressurized compaction  permeameters with
an air-induced elevated hydraulic gradient were used.  For  two montmoril-
 lonite clays,  a gradient of 361.6 (equivalent to a hydraulic head of 42.2 m
of water) was used.  For the illite and kaolinite clay soils, a hydraulic
gradient of 61.6 (equivalent to a hydraulic head of  7 m of  water)  was
 imposed.  No signs of particle migration or turbulent flow  resulted from the
elevated gradients.
                                    4-39

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                                          +  Carbon  Tetrachlorfde
                                          o  Xylene
                                          A  Trichloroethylene
                                          •  Deiom'zed Water
                                          0  Glycerol
                                          x  Acetone
                                          A  Methano1
50 i
      £52; Carbon Tetrachlorid
                        10
                                                                    30
                                      15         20         25

                                        Time (day)

Source: Green, Lee, and Jones, 1979


      Figure 4-4. Coefficient of permeability of Ranger shale to various chemicals.
25
                                4-40

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      TABLE 4-9.  GRAIN SIZE DISTRIBUTION,  MINERALOGY,  AND  PROPERTIES
                          OF THE EOUR CLAY  SOILS*

Clay soil
description
% Sand (>50 nm)
% Silt (50-2.0 nm)
% Clay (<2.0 nm)
Coarse clay (2.0-0.2 nm)
% of total
Mineralogy'3
Fine clay (<0.2 nm)
% of total
Mineralogy0
Cation exchange capacity
(meq/100 g)
Total alkalinity (meq/100
Fe203 (%)
Organic matter (%)
CaC03 Equiv. (%)
Shrink-swell potential
Liquid limit
Plasticity index
Optimum water content0
Maximum density (kN rrr3)
Non-
calcareous
smectite
35-37
26-28
36-38
16
QZ-1
KK-2
MI-2
84
MT-1
24.2
g) 3.3
0.42
0.9
-
Very high
51-67
30-45
20.0
15.0

Calcareous
smectite
7-8
42-44
48-50
25
MT-1
KK-2
QZ-3
75
MT-1
KK-3
36.8
129.2
0.2
3.0
33
Very high
*
58-98
34-72
21.5
14.4
Mixed
cation
kaolinite
39-41
17-18
42
33
KK-1
QZ-2
67
KH-1
MT-3
8.6
0.8
13.2
0.6
Trace
Moderate
41-60
18-30
20.0
16.3
Mixed
cation
illite
14-15
38-39
47
61
1-1
QZ-2
39
1-1
MT-2
18.3
4.2
-
-
-
Moderate
-46
-27
19.0
16.6
aAdapted from Anderson, 1981.
DKey to mineralogy: MT =
KK =
I =
Smectite 1
Kaolinite 2
Illite 3
= >40% QZ
= 10-40% MI
= <10% KH
= Quartz
= Mica or il
= Halloysite
lite

cPercent by dry weight.
                                    4-41

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      Special  precautions were taken to minimize several  sources  of  error  that
 occur frequently 1n permeability testing.   At least  one  pore  volume of  the
 CaS04 solution was passed through the soil  cores to  minimize  trapped
 air.  Before  the permeameter was pressurized, the top  of the  soil sample
 was exposed to 10 cm of standard CaS04 solution for  48 hours.  This
 procedure helps to prevent channel  formation  and bulk  flow  and promotes
 sealing of the permeameter sidewalls.  Provision was made to  view the efflu-
 ent passing through the soil sample so that trapped  air  or  evidence of  piping
 could be monitored.  Care v/as taken to minimize evaporative losses  from the
 collected effluent.  Teflon  fittings were  used wherever possible to avoid
 deterioration from exposure to the  organic  solvents.

      After seating the soils at low pressure, the selected  gradient was
 applied to the permeameter fluid chamber .until  stable  permeability  values
 were obtained with the standard CaS04 solution.  At  this point,  pressure
 was released  and permeameters were  disassembled.  Soil that had  expanded
 out of the mold was removed and additional  standard  leachate was passed
 through the remaining sample in the permeameter.  Percent swelling  was  deter-
 mined for each soil.   At this point,  the soil  sample was assumed to be  com-
 pletely saturated.

      After the saturation step to ensure stable baseline permeability,  the
 remaining standard CaS04 solution was removed and  replaced  with one  of
 the organic solvents  to be tested.   The  selected gradient was imposed and
 between 0.5 and 2.0 pore volumes  of fluid were  passed  through the sample 1n
 the permeameter.   The permeameters  were  then  depressurized, disassembled, and
 the cores removed  and examined for  evidence of  structural changes.   Following
 the permeability tests  of the noncalcareous smectite clay soil with aniline,
methanol,  and  ethylene  glycol  (all  highly water-soluble), water was  reintro-
duced  to  the test  columns  and permeabilities were again  determined.

     During the permeability  tests, effluent was carried to an automatic
fraction  collector, which  separated the  samples  obtained from 10 permeameters
during  specific time  increments.  The percentage of organic fluid in the
effluent  samples was  determined to develop breakthrough  curves.  A permeabil-
ity value,  leachate volume, and time  increment were obtained on each volume
of  fluid  passed through a  sample.

 4.5.9.2  Test Results--
     Baseline permeability  (two pore volumes)  for the four soils  is  depicted
1n Figure 4-5.  Permeability data obtained for the various organlcs  tested
are presented 1n Figures 4-6  through 4-13 (Anderson,  1981; Anderson  et  al.,
1981; Brown and Anderson,  1983).  Findings as  described by the authors  are
excerpted below:

     Acetic Acid (glacial)—All four clay soils permeated with acetic acid
     showed initial decreases  in permeability  .  . . thought to be due to
     partial dissolution and  subsequent migration of  soil particles. These
     migrating particle fragments could lodge  in the  fluid-conducting pores,
     thus decreasing cross-sectional area available for fluid  flow.
                                    4-42

-------
o
-J


-------
                            NCNCALCAREOUS   SMECTITE

                            CALCAREOUS   SMECTITE

                            MIXED CATION  KAOLJN1TE
                            MIXED CATION I LUTE
                                       ACETIC AGO
                   as      to      1.5
                      PORE  VOLUMES
Source: Anderson, 1981


          Figure 4-6. Permeability of the four clay soils to acetic acid.
                          4-44

-------
   100-

LU  ^  4-
s  B  t
-»-!-»  ••
               I
              LU
             NCNCALCAREOUS   SMECTITE
             CALCAREOUS   SMECTITE
             MIXED  CATION  KAOLJNITE
             MIXED  CATION  ILL1TE
                                                          A
                                                          o
      0.5
ao
as      LO      1.5
   PORE  VOLUMES
2.0
2.5
    Source: Anderson, 1981
            Figure 4-7. Permeability and breakthrough curves of the four clay
                          soils treated with aniline.
3.0
                             4-45

-------
                           NONCALCAREQUS  SMECTITE
                           CALCAREOUS • SMECTITE.
                           MIXED  CATION   KAOUNITE
                           MIXED  CATION  I LUTE
                               ETHYLENE GLYCOL
                   0.5      L'0.     1.5
                     PORE  VOLUMES
Source: Anderson, 1981

         Figure 4-8. Permeability of the four ciay soils to ethylene glycoi.
                         4-46

-------
                         NCNCALCAREOUS   SMECTITE
                         CALCAREOUS  SMEC
                         MIXED  CATION  KAOUNITE
                         MIXED  CATION  ILL1TS
                                       ACETONE
IO
                  as      to      1.5
                    PORE  VOLUMES
 Source: Anderson, 1981.
            Figure 4-9. Permeability of the four clay soils to acetone.
                       4-47

-------
 <


'LU
    100-
B    ::
  LU
  !z   -
                f
                i
               LU
                            NCNCALCAREOUS  SMECTITE

                            CALCAREOUS  SMECTITE

                            MIXED CATION* KAOUNITE

                            MIXED CATION  1LLJTE
                                            METHANOL
                                                              A


                                                              O
    10
      CL5
            ao
as      to'      1:5
   PORE  VOLUMES
2.0
2.5
3.0
 Source: Anderson, 1981
    Figure 4-10. Permeability of the four clay soils to methanol and the breakthrough
            curve for the methanoi-treated mixed cation illitic clay soil.
                             4-48

-------
     as       ao      as       to       i.s
                            PORE   VOLUMES
2,0     2.5
3.0
Source: Anderson, 1981
    Figure 4-11.  Permeability of the methanol-treated mixed cation illitic clay soil
                         at two hydraulic gradients.
                              4-49

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                             NCNCALCAREOUS  SMECTITE

                            : CALCAREOUS  SMECTITE

                             MIXED  CATION   KAQLiNITE
                             MIXED  CATION  I LUTE
               A

               O
                                            XYLENE
                    0.5     :|.0      1.5
                       PORE  VOLUMES
2.0
2.5
3.0
Source: Anderson, 1981
        Figure 4-12. Permeability and breakthrough curves of the four clay
                      soils treated with xylene.
                        4-50

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  100-
                          NCNCALCAREOUS   SMECTITE

                          CALCAREOUS  SMECTITE

                          MIXED  CATION   KAOUNITE
                          MIXED  CATION  I LUTE
                                            HEPTANE
    0.5
ao
0.5      10      1.5
   PORE  VOLUMES
2.0
Z.5
3.0
Source: Anderson, 1981
        Figure 4-13. Permeability and breakthrough curves of the four ciay
                      soils treated with heptane.
                          4-51.

-------
 Two  of  the  soils  treated with acetic acid  (calcareous smectite and mixed
 cation  kaolinite)  showed continuous permeability decreases throughout
 the  test  period.   After passage of approximately 20 percent of a pore
 volume, the acid  treated kaolinitic clay generated a dark red-colored
 effluent  .  .  . probably due to dissolution of iron oxides.  The acid
 treated calcareous smectite began passing  cream-colored foamy effluent
 after passage of  about 28 percent of a pore volume. . . . The creamy
 material  was probably dissolved calcium, while the foam was the result
 of C02  liberation  from the dissolved carbonates.
 Both noncalcareous smectite and the mixed  cation illite eventually
 showed permeability increases after . . .  passage of 39 percent and 62
 percent of  a pore  volume, respectively. .  . . Permeability increases
 with both of these soils were probably due to progressive soil piping
 that eventually cleared initially clogged  pores.
 Aniline—Both noncalcareous smectite and mixed cation ill He had
 breakthrough of aniline with concurrent permeability increases at pore
 volume values (below 0.5). . -. . Aniline broke through after passage of
 one pore  volume for the kaolinitic soil.  The calcareous smectite . . .
 permeability increased rapidly at first, but showed substantial de-
 crease concurrent  with aniline breakthrough.  After the permeability
 decrease, this soil  exhibited a slow but steady permeability increase.
 There were  no signs  of migrating soil  particles in any effluent
 samples.  .  . . Apparently, aniline is too weak a base to cause signifi-
 cant dissolution of clay soil components.  However, . . .  the organic
 base caused extensive structural changes in the upper half of the soil
 cores.  The massive  structure of the four  soils . . . was altered by
 aniline into an aggregated structure characterized by visible pores and
 cracks in the surface of the soils.
 Ethylene  Glycol—  .  . . Permeability values indicated that it was the
 ability of  ethylene  glycol to alter ;the soil fabric that was the domi-
 nating influence on  permeability.  Three of the clay soils treated with
 ethylene  glycol showed initial permeability decreases.  The kaolinitic
 clay soil continued  to undergo permeability decreases as long as it was
 being tested.  The illitic clay soil began showing a permeability in-
 crease after passage of 0.5 pore volumes.  In contrast, the calcareous
 smectite  followed  its initial permeability decrease with a substantial
 increase, a second decrease, and finally reached a nearly constant value
 that continued until the end of the test period.
 The noncalcareous  smectitic clay soil  treated wfth ethylene glycol
 showed an initial  rapid increase in permeability and a slower but con-
 tinuous increase after passage of 0.5 pore volume.
Acetone—All soils  treated with acetone had initial  permeability de-
 creases.  These decreases continued until  passage of approximately 0.5
 pore volume.  During passage of the next 0.5 pore volume, however, the
 soils underwent large permeability increases.  One possible explanation
 for this  sequence  of permeability changes is as follows:
 1.   The  higher dipole moment of acetone caused Initial  Increase in
     Interlayer spacing between adjacent clay particles as compared to
     water only.
2.   As more acetone passed through the soil cores,  more water layers
     were removed  from clay surfaces.   Due to its larger molecular
     weight, however, fewer acetone layers were adsorbed than had
     adsorbed when water was the only  fluid present.  This resulted 1n a
     larger effective cross-sectional  area available for fluid flow.
                               4-52

-------
      While acetone can displace water from clay surfaces  due  to  its  higher
      dipole moment, it cannot fgrnKas many adsorbed  fluid layers as  water due
      to its higher molecular weight.        '
      Examination of the soil  after acetone treatment showed extensive  shrink-
      age and cracking.  Such soil  shrinkage is  usually  associated with de-
      hydration,  indicating that acetone  had extracted water from soil
      particle surfaces.
      Methanol—Unlike soils treated with acetone, methanol-treated soils
      underwent no initial  permeability decrease.
      Percent methanol in the effluent from the  illitic  clay soil paralleled
      an increase in permeability of the  soil.   After passage  of 1.5  pore
      volumes, the hydraulic gradient  was reduced from 61.1 to 1.85 and
      another pore volume of methanol  passed.  After  an  initial decrease,
      permeability of the soil  steadily increased at  the lower hydraulic
      gradient. ... No particle migration was  detected in effluent  from
      methanol-treated cores,  and therefore soil piping  was discounted as
      a mechanism for observed permeability increases.   Examination of
      methanol-treated soil  cores revealed development of  large pores and
      cracks visible on the soil  surface.  The lower  dielectric constant of
      methanol may have caused a decrease in interlayer  spacing of the clay
      minerals present in the  soils and thereby  promoted the structural
      changes.
      Xylene—Xylene-treated soils  showed rapid  permeability increases fol-
      lowed by nearly constant permeabilities roughly two  orders of magnitude
      greater than their permeabilities to water.  Permeability increases
      may be caused by ... structural changes  in the xylene-treated soils,
      exemplified by massive structure before treatment  and blocky structure
      after the soils were  treated  with xylene.
      Heptane—Permeabi 11 t.v patterns for  the heptane  cores  closely approxi-
      mated those shown by  the xylene-treated cores (i.e.,  large initial per-
      meability increases).   Following these initial  large  increases, rate of
      permeability increase slowed  until  nearly  constant permeability values
      were observed.
      Only the calcareous smectitlc clay  showed  . . . permeability to heptane
      well  below  its  permeability to xylene.  The constant permeability values
      eventually  reached  by the  neutral nonpolar treated cores were probably
      related to  the  limited ability of these fluids  to  penetrate interlayer
      spaces of the clay minerals.                    ,

4.5.9o3   Reintroduction  of  Water--
      When the standard  calcium  sulfate solution was  reintroduced to the non-
calcareous  smectite  test columns permeated with aniline, methanol, and
ethylene  glycol,  a subsequent decrease in  the permeability (roughly 1 order
of magnitude)  was  observed.  The final permeability  (after one pore volume of
standard  solution)  remained well above the  baseline permeability measured
prior to  introduction  of the organic  solvents (Anderson, 1981).

4.5.9.4   Discussion-
      Viscosity and density differences between the organic fluid and water
do not account for the large changes  in permeability observed 1n the tests.
The data  from  these permeability tests illustrate the importance of passing
multiple pore volumes of fluid through the soil  samples  in order to determine
the effects of solvents on permeability.
                                    4-53

-------
      The work by Anderson  has  been  criticized as being  "unrepresentative of
 real  conditions" because pure  organic  solvents  (rather  than waste leachate)
 were  used in the permeability  tests (Gray and Stoll,  1983).  The test results
 stand,  however,  as  a demonstration  of  potential effects on clay liners should
 they  come in contact with  certain types  of  undiluted  organic liquids.

      The high gradients  used in  the tests have  also been questioned (Zoeller,
 1982; Gray and Stoll, 1983) since it is  unlikely that gradients as high as
 361 would be encountered in the  field.   The use of elevated gradients in
 laboratory testing  in order to reduce  testing time is not uncommon.  Although
 the gradients used  by Brown and  Anderson were higher  than those used by most
 researchers, the permeability  changes  observed  cannot be attributed to the
 elevated gradients.   Conditions  were maintained well within the laminar flow
 regime  (I.e., Reynolds number  was below  10) so  that Darcy's Law for computing
 the permeabilities  remained valid.   In general, the trends observed in these
 tests are consistent with  data from other researchers, and explanations can
 be linked to the findings  from clay-chemical complex  studies.

      Complete saturation in the  compaction  permeameter without backpressure
 cannot  be ensured.   It is  possible  that  air introduced with the permeant
 fluids  could have influenced the test  results to some extent, but probably
 by no more than  1 order  of magnitude.

      Finally, the use of fixed-wall  permeameters for these studies has been
 criticized (because  of the potential for sidewall leakage) by advocates of
 trlaxlal  test methods.   As there are advantages and disadvantages with either
 method,  the argument as  to which test  is most meaningful is finally a matter
 of opinion.

      Acetic acid, a  weak organic acid, has  a dissociation constant of
 1.75  x  10-b in aqueous solution  (pKa = 4.75) at 25°C.  Since glacial
 acetic  acid was  used,  the  extent of ionizatlon was a fraction of this.  The
 permeability decreases observed  probably would  have been followed by sharp
 increases  In permeability  due  to dissolution of the basic soil  components if
 a dilution  had been  used rather  than glacial acetic acid.  Progressive
 soil  piping,  as  pointed  out by Brown and Anderson, follows the soil  dissolu-
 tion  and  eventually  results in large pores with an associated increase in
 permeability.
                                                    «

      This  effect  (i.e.,  increased permeability) is to be expected with
 carboxylic adds  or  sulfonic acids  in general.  This is of particular
 significance  since carboxylic  acids  are among the biological  degradation
 products of  a wide range of organic  compounds.  Soils that are high  in
 carbonates are most affected by  acids (even weak acids such as  acetic acid),
 but other  soil constituents such as  Fe£03 are also susceptible.

 4.5.10  Schramm's Study  (1981)  of the Permeability of Soil  to Organic
        Solvents

     Schramm  (1981)  evaluated permeabilities for eight soils  tested  with
kerosene, Isopropyl  alcohol,  ethylene glycol,  and mixed xylenes.
Permeability with water was also measured.   A total  of 211  column  tests  were
 run to determine saturated  permeabilities to the various test fluids.  The
research was performed at the University of Arizona.
                                    4-54

-------
      Clay content in  the  soils  ranged  from  1  percent  in River Bottom sand to
 70 percent in-Lake Bottom clay.   Characteristics of the soils are presented
 in Table  4-10.                 '   •**        -*   '

 4.5.10.1   Test  Method--
      Permeabilities were  obtained in glass  or plexiglass cylinders through
 the falling  head  method.   Cylinders 5.8 cm  in diameter were used in the tests
 with soil  packed  to a depth  of  5  cm.   Soil  was  retained in the cylinders by a
 galvanized screen glued to the  cylinder.  Prior to testing, samples were
 immersed  overnight in the test  solvent.  During the test, the height of the
 solvent column  above  the  soil surface  varied  between  6 and 2 cm.  Six
 replicates were tested for every  solvent-soil  combination.  Experiments were
 repeated  until  a  constant permeability value  was obtained.  Length of runs
 varied from  1-1/2 minutes to several weeks.   An analysis of variance was
 performed  to evaluate differences  between intrinsic permeability for the
 various soils and solvents.

 4.5.10.2   Test  Results—
     A summary  of the saturated permeability  values (expressed in cm/h)
 obtained from these tests is given in  Table 4-11.  It is notable that with
 each soil  tested  the  highest permeabilities were obtained with the non-
 polar organics, kerosene,  and xylene.  (Kerosene is a mixture of Ci2-Ci«
 compounds  and includes both aliphatics and aromatics.)

     Intrinsic  permeabilities were also calculated to take into account
 differences  in  viscosity  and density for the  various permeant fluids.
 Analysis of  the intrinsic  permeability values Included a one-way variance
 test to determine  if  the  intrinsic permeability varies significantly with
 solvents or with  soils.   The intrinsic permeabilities for a given soil  are
 expected to be  constant unless there is interaction between the soil  and the
 permeating liquid.  The differences in intrinsic permeability with the
 different  solvents are shown in Figure 4-14 for five soils.  The trend  for
 increased  intrinsic permeability is readily apparent.

     The analysis also shows rather uniform behavior of intrinsic perme-
ability for solvents  in the different soil  types,  the  Fanno,  Mohave,  and
River Bottom Sand having highest relative intrinsic permeabilities with all
organic solvents.

     From the data summary and analysis of  variance,  Schramm  (1981)  concluded
that:

     Calculated values of intrinsic permeability vary  for  the  same soil
     depending on solvent.  However,  the  variation  is  relatively minor  com-
     pared to variation due to differences  in  soil  properties  among  several
     soils. ...

     Since intrinsic permeability values  vary  for  the  same  soil  depending  on
     solvent, the  soil and solvents are interacting.
                                    4-55

-------
                            TABLE 4-10.   CHARACTERISTICS  OF  SOILS  USED  IN  PERMEABILITY TESTS3
Soil name
Lake Bottom clay

Nicholson
Fanno

Chalmers

"f1 Canelo
en
O) .
Anthony

Mohave

River Bottom sand


Soil
order
Entisol

Alfisol
Alfisol

Mollisol

Alfisol

Entisol

Aridisol

Entisol


Electrical
Cation conductivity
Soil exchange of saturated
Clay Silt Sand paste capacity extract
% % % pH (meq/100 g) (emho/cm)
70.6 24.0 5.4 7.7 34.7
-
49.0 47.0 3.0 6.7 37.0
46.0 19.0 35.0 7.0 33.0

31.0 52.0 14.0 6.6 22.0

28.0 28.6 43.4 5.6 5.76

15.0 14.0 71.0 7.8 10.0

11.1 37.0 52.0 7.3 10.0

1.0 2.0 97.0 7.2 2.0

t
1,111

176
392

288

240

328

615

210


Column
bulk
density
(g/cm3)
1.52

1.53
1.48

1.53

1.72

.1.87

1.78

1.80


Soil
surface Predominant
area cl ay
(m^/g) minerals
142.0 11 lite
Kaolinite
120.5 Vermiculite
122.1 Montmorillonite
Mica
95.6 Montmorillonite
Vermiculite
35.0

49.8 Montmorillonite
Mica
38.3 Mica
Kaolinite
3.6 Kaolinite
Mica

aAdapted from Schramm (1981).

-------
                      TABLE 4-11.  PERMEABILITY COEFFICIENTS  (cm/s) DETERMINED  IN  SOILS  TESTED WITH
                                                   ORGANIC SOLVENTS9
CJl
•vl
Soil
Lake Bottom clay
Nicholson
Fanno
Chalmers
Canelo
Anthony
Mohave
River Bottom sand

Water
5.0 x 10'5
4.2 x 10~6 "
.1.5 x 10-4
1.8 x 10-5
5.0 x 10-6
9.9 x ID"5
1.9 x ID'3
1.7 x 10-2

Kerosene
3.4 x ID"4
9.5 x 10-5
5.2 x 10~3
3.8 x ID'5
5.6 x 10-5
2.0 x ID'4
2.6 x ID'3
3.4 x ID'2
Solvent
Isopropyl
alcohol
2.1 x 10-4
2.3 x 10-5
3.1 x 10-3
2.3 x lO-5
3.5 x 1C-5
9.5 x ID'5
1.6 x ID'3
5.8 x 10-3

Ethyl ene
glycol
1.1 x 1C-5
6.8 x 10~7
3.0 x ID'4
1.8 x ID'6
1.4 x 10~6
5.8 x 10'6
2.0 x ID'4
6.4 x ID'4

Xyl ene
1.7 x 10-3
3.5 x ID'4
1.8 x lO-2
1.7 x ID'4
1.5 x 10-4
4.4 x ID'4
8.5 x 10-3
1.8 x ID'2
       aData from Schramm (1981).

-------
14
12-
10-
8.
6
4-
2



LAKE BOTTOM dAX




^_^










••MOM





•«•••









•H^B"






1
Kay:


f

]
                                        WATR - Water
                                        ETGL • Ethelyne Glycol
                                        ISO? • Isopropyl
                                        KERO « Xerosine
                                         XYL « Xylene
    u
    a,
    o   4.
    UJ
    I   3

    i   »
             NICHOLSON
                   n
                                      ANTHONY
nn
        2 ,
CHALMERS
I^H^H^

CANELO
••^•H
n
          WATR ETGL ISOP KERO  XS.     WATS ETGL ISO? KERO XXL

                              SOLVENTS
Source: Schramm, 1981

       Rgure 4-14. Variation of intrinsic!permeability with solvent for each soil.
                             4-58

-------
 4.5.10.3  Discussion—
      The test method  used  by Schramm differed significantly from that
 employed by Anderson  (1981)  to measure permeability.  Notable differences
 include the following:

      •   Gradients  imposed  on the  sample were very low.

      •   No estimate was made of the pore volumes passed through the test
         samples.

      •   Samples were  presaturated with the test fluid rather than a standard
         calcium-sulfate solution.

      The impact of the low hydraulic gradient on the test results is not
 known.   The concept of "threshold gradient" has been postulated, although
 there is no evidence  of this effect in the results reported by Schramm.

      Although Schramm reports that tests were continued until constant per-
 meability values were obtained, the criterion to establish an acceptable
 difference in consecutive  measurements was not discussed.  There is no indi-
 cation  of the number  of pore volumes exchanged.

      It may be argued that saturating the samples using the test permeant
 fluid rather than  water or a standard permeant solution is representative of
 conditions typical for a liner in service in a land disposal application.

 4.5.11   Evaluation by Monserrate  (1982) of the Permeability of Two Clays
         to Selected Electroplating Wastes

      Monserrate (1982) at  Duke University investigated the permeability of
 two clays  exposed  to  simulated electroplating wastes.  The purpose of the
 research was  to examine the  effect of compaction on the permeability response
 of the  two clays.  The clays  tested were a Wyoming bentonite and a White
 Store clay from North Carolina.  The White Store clay was reported to be an
 active  clay.

      The  simulated electroplating wastes used as permeant fluids were a
 1-molar solution of zinc chloride (ZnCl2) (136.3 g/L, pH = 5.5)  and a
 1-molar solution of chromic  acid (t^Crtty) (100 g/L, pH = 1.5).

 4.5.11.1   Test Method--
      Standard  Proctor tests were conducted on each clay to establish the
 relationship  between water content and compacted density.  Procedures
 outlined  in ASTM D-698 Method A (ASTM 1985)  were followed.  Permeability
 studies were  subsequently conducted at several  different moisture contents.

      For the permeability tests,  the samples were prepared by mixing 0.01 N
 calcium sulfate with the clay to achieve the desired moisture content.   The
 clays were compacted into either zinc-plated or lucite compaction permeam-
 eters using compactive efforts comparable to those used in the standard
 Procter tests.  The compaction permeameters  measure 4 inches (10.16 cm) in
diameter and 4.6 inches  (11.68 cm) in  height.   Clays were compacted to  a
depth of 2 inches   (5.08  cm).   The  compaction permeameters were adapted  to
                                    4-59

-------
 allow measurement  of  flow as  the permeant fluid enters the unit.  The data
 were evaluated as  a falling head test.  A standard solution of deaired 0.01 N
 calcium  sulfate was used to saturate the sample prior to introducing the test
 permeant fluids.   The samples were exposed to the permeant fluids under
 approximately 75 pounds of air pressure.  In the permeability tests,a
 statistical procedure was used to determine when enough data had been
 accumulated to make a determination of the k value for a certain clay-
 permeant fluid combination.   (See details in Section 4.3).

 4.5.11.2 Test Results-

     Tests with bentonite showed that at imoisture contents in the proximity
 of the optimal compacted moisture content, permeabilities to calcium sul-
 fate, chromic acid, and zinc chloride were all on the order of 10~10
 cm/s.  At lower moisture contents, the permeability to calcium sulfate was
 higher by a factor of 2 than the permeability to the chromic acid test
 solution.  At wet-of-optimum water-contents, however, the permeabilities
 determined for the two fluids were nearly identical.  The same low water
 content  divergence in  permeability was observed for the zinc chloride test
 fluid, although the magnitude of the difference was less.

     The permeability of White Store clay to standard calcium sulfate solu-
 tion and to the test  fluids is shown in Figure 4-15 as a function of the
 moisture content at compaction.  The White Store clay appeared to be more
 sensitive than the bentonite clay to changes in compacted moisture content.
 The permeability to the chromic acid test fluid aligns closely with that of
 calcium  sulfate at moisture contents higher than about 20 percent (optimum
 moisture content = 21.5 percent).  At lower than about 20 percent moisture,
 the permeability to the chromic acid was higher than to calcium sulfate.
 Zinc chloride test fluid showed permeabilities lower than for calcium sulfate
 at low moisture.

     Monserrate (1982) concluded that for both bentonite and White Store
 clays, the application of zinc chloride and chromic acid did not alter the
 clay's permeability response, indicating that the structure of the clay, as
 compacted, is the  predominant influence in determining permeability.  She
 noted that the test results differed markedly from those of Cola (1981) who
 carried out similar studies at Duke University using the chromic acid.

     Monserrate noted that there was extensive corrosion of the steel per-
meameters and some of the pressure fittings that were exposed to the chromic
 acid test fluid.

4.5.12  Research by Brown. Green, and Thomas (1983) on the Effect of Two
        Organic Hazardous Wastes on Simulated Clay Liners

     Brown, Green, and Thomas (1983) at Texas A & M University reported
 results of permeability tests in which clay soil  samples representative of
three types of simulated clay liners were subjected to a xylene waste and an
acetone waste in both laboratory and field studies.  The three clay materials
tested were predominantly kaolinite, mica, or bentonite.  The soils were
blended with sandy loam soil  to attain permeabilities in the range of
1 x 10~7 to 1 x 10-°.  The laboratory studies in  fixed-wall  permeameters
                                    4-60

-------
o>
                       3.6 X 10
                              ,-7
                               ,-7
                       3.0 X 10
                   ~   2.4 X 10"7
                   fj
                   1   1.8 X 10~7
                   Q)
                   Q.
                               -7
                       1.2 X 10
                       6.0 X 10~8
                                                              Moisture Content at Compaction (%)
                           Source: Monseratte, 1982
                                     Figure 4-15.  Permeability of White Store clay to 0.01 N calcium sulfate, chromic acid
                                        (1 molar), and zinc chloride (1 molar) as a function of moisture at compaction.

-------
 were directed at determining the influence of different initial  moisture
 contents andjelevated gradients on the clay permeabilities.  The procedures
 used in the laboratory tests were similar to those described by  Anderson
 (1981) and Brown and Anderson (1983) in earlier permeability tests with
 organics.  The research was sponsored by the U.S. EPA.

      The xylene waste, a paint solvent that was used to clean factory sprayer
 lines, contained 25 percent paint pigments and trace amounts of  water.  The
 acetone waste was a chemical manufacturing waste containing 91.7 percent
 acetone, 4 percent benzene, 0.6 percent phenol, and 3.7 percent  unknown.

 4.5.12.1  Test Methods—
      For the laboratory tests, soils were compacted wet of optimum to at
 least 90 percent Proctor density.  Prior to exposure to the waste solvents,
 samples were saturated with 0.01 N calcium sulfate.  Unsaturated cores were
 also subjected to the permeability tests.  Pressures of 5, 15, and 30 psi
 (equivalent to hydraulic heads of 31, 91, and 181)  were tested.

      Twenty-eight field cells (1.5 m x 1.5 m x 1.8  m inside dimensions)  were
 constructed of reinforced concrete and lined with 100-mil  high-density
 polyethylene to facilitate leachate collection.  The clay  soils  were  com-
 pacted  with a vibratory compactor to 95 percent Proctor in two 7.5-cm-thick
 lifts.   The liquid  waste  to be tested was introduced into  each cell through a
 standpipe  Into barrels  that were placed above the liners.   A head  of  1 m of
 liquid  (gradient  of 7)  was maintained throughout  the test.   Permeabilities
 were calculated based on  the volume of cell  drainage collected during dis-
 crete time  intervals.   Following the  permeability tests, each cell was dis-
 assembled and  subjected to chemical  and morphological analysis.  The wastes
 to be tested  in the field  cells  were  dyed with  Automate Red  B and  Fluorescent
 Yellow  to facilitate detection within the sample  cores.

 4.5.12.2   Laboratory Test Results—
      To  compare the results  from the  various  tests,  calculated permeabilities
 were  plotted as a function  of  the number  of  pore  volumes of  effluent that
 passed  through  the  sample.   Permeabilities to standard calcium sulfate solu-
 tion  on  similar soils in the  laboratory were  generally found to be repro-
 ducible  to within 0.25  order of magnitude.   Permeabilities  increased, how-
 ever, when  the organic-solvent wastes were substituted as the permeant
 fluids.  Permeability to the organic-solvent wastes was typically 2 to 4
 orders of magnitude  greater  than the  permeabilities measured with the calcium
 sulfate  solution.   Presaturation with 0.01 N  calcium sulfate appeared to
 retard the effect of the permeant fluids  on  the samples (I.e., more pore
 volumes were displaced before breakthrough occurred  1n the presaturated
 samples).  Highest  permeabilities measured on initially unsaturated samples
were  typically  1 to  2 orders of magnitude greater than for samples that were
 Initially saturated.

      Permeability of the clay soils increased rapidly upon exposure to xylerie
waste after the cumulative flow exceeded 0.2 to 0.4 pore volume.   The behav-
 ior of acetone was  characterized by an  Initial small decrease 1n  permeability
 (minimum at approximately 0.5 pore volume), which was followed by a steady
Increase In permeability.  This behavior was explained as follows:  acetone
first caused swelling of the clay soil with low concentrations Initially
                                    4-62

-------
 diffusing  into  the  pores;  as more of the water was displaced by the solvent,
 shrinkage  occurred.
             —         •         t  .3.--    ' • • m.  s
                                  -:*v         •: *
      Similar increases  in  permeability were  observed for all three soil
 types.   The increase  in  permeability, however, for the bentonite samples
 occurred after  a  larger  pore volume was displaced.

      If  the permeability values  calculated  from the test data are plotted as
 a  function of pore  volumes, the  different hydraulic gradients used in the
 experiments (31,  91,  181)  have  little influence on either the increase in
 permeabilities  observed  or on the final values achieved.  (This conclusion
 holds for  both  presaturated and  unsaturated  samples [Brown et al., 1984]).

 4.5.12.3  Field  Test Results—
      In  the field studies, xylene had penetrated 10 of the 12 clay liners
 within 12  months  after  installation; acetone had penetrated 2 of the liners
 but at a slower rate.  Increases in permeability of the bentonite clay soil
 to xylene  were  more dramatic (as much as 2 orders of magnitude increase) than
 of the other soils and occurred  after passage of 0.5 pore volume of permeant
 fluid.   Kaolinitic and micaceous soils showed immediate increases in perme-
 ability  to xylene.  Permeability values continued to increase as more pore
 volumes  of fluid  passed  through  the sample.  Increases of more than 2 orders
 of magnitude were observed in some samples after passage of two pore volumes
 of xylene.

      Field tests  with the acetone waste exposed to micaceous clay soil  showed
 a permeability  decrease with the first 0.5 pore volume.  This was followed,
 however, by an  increase  in permeability.  After two pore volumes had passed
 through  the liner, the permeability was slightly higher than the initial
 value measured.

      Visual inspection of the clay liners following permeation by the liquid
wastes was facilitated by the dyes and by the paint pigment in the xylene
waste.   Dyed surfaces observed throughout the liner Indicated that the  liquid
 had moved through the soil  through preferential  channels rather than in a
 clearly  defined wetting front.  Preferential channels were occasionally found
 to extend from  the top to the bottom of the liner.   Evidence that xylene
moved through cracks  in the liner or around blocky  subangular structural  com-
 ponents was also  obtained through chemical  analysis of sections of the  per-
meated liners.   The channels observed in the clays  are attributed to the
displacement of water by the chemicals resulting in desiccation that caused
 the clay to shrink and crack.

 4.5.12.4  Discussion—
     The results  of this study,  in close agreement  with those previously
 found by Brown  and Anderson (1983),  indicate that severe permeability in-
 creases  can occur when certain clay materials are in contact with concen-
 trated organic  solvents.  Although the hydraulic heads used in the laboratory
test procedures are higher than  are likely to be encountered in the field,
the data suggest  that the permeabilities measured are independent of the
hydraulic gradient used in the test.  These results further support the
conclusions by  Anderson based  on tests involving a  gradient of 361.
                                    4-63

-------
      The effect of presaturatlon  with  calcium sulfate on  the highest perme-
 abilities 1s .significant.   Laboratory  tests  by other researchers  (Green
 et al.,  1979;  Foreman and  Daniel, 1984)  have also  involved  introducing the
 test permeant  fluid onto the unsaturated sample.

 4.5.13  Study  by Brown.  Thomas, and  Green (1984) of the Effect of Dilutions
         of Acetone and Mixtures of Xylene and Acetone on  Permeability of a
         Micaceous Soil

      To  determine the effect of diluting a polar organic  solvent with water,
 Brown, Thomas,  and Green (1984) measured the permeability of an unsaturated
 micaceous compacted soil to several  acetone-water  dilutions.  Samples were
 tested at a gradient of  91 in laboratory tests with fixed-wall permeameters.
 Solutions tested were 100, 75, 50, 25,  12.5,  and 2 percent  acetone.  Methods
 were similar to those used previously  by Anderson  (1981).

      Compared  to permeability to  water (actually 0.01 N calcium sulfate), an
 Increase in permeability was seen for  solutions where the concentration of
 acetone  was 75  percent or  100 percent.   Samples permeated with lower concen-
 trations of acetone did  not show  appreciable changes compared to the perme-
 ability  to water.

      Similar tests were  conducted to determine the effect on permeability of
 mixtures of xylene and acetone (Brown  et al.,  1984).  For 100 percent xylene,
 the  permeability was reported to  be  4  orders  of magnitude greater than the
 permeability to water (0.01 N calcium  sulfate).  When a mixture of 87.5 per-
 cent xylene and 12.5 percent acetone was tested, the permeability was dramat-
 ically reduced  (i.e.,  more than 3 orders of magnitude below the permeability
 to pure  xylene).   Values were comparable for  a mixture containing 25 percent
 acetone  and 75  percent xylene and for  a  1:1 mixture.  When  the acetone compo-
 nent was increased to  75 percent,  however, the permeability increased to
 approximately the value  obtained  in  similar  tests  with pure acetone.  This
 value was  about 1.5 orders of magnitude  greater than the  permeability of the
 sample to  0.01  N calcium sulfate.

 4.5.14  Tests by Brown. Thomas, and  Green  (1984) to Determine the
         Permeability of Micaceous Soil to: Petroleum Products

      Brown,  Thomas,  and Green  (1984) also; reported permeability tests with
 five  commercial  petroleum  products.  A compacted micaceous soil,  unsaturated,
was  permeated with  the test  fluids at a  gradient of 91.  The results of the
 tests  with  kerosene, diesel  fuel, paraffin oil, gasoline,  and motor oil  are
 shown  in Figures  4-16 through 4-20,  respectively.  Conclusions of the tests
 show  that the micaceous soil  is more permeable  to  these petroleum products
 than  to water (0.01  N calcium sulfate).

      In  tests with  kerosene, the permeabilities were 3 to  4 orders of magni-
tude  higher  than  values measured with 0.01 N calcium sulfate in similar
 samples.  One-half  the difference was achieved within the  first 0.1 pore
volume.  The permeability  to paraffin oil was about 1 order of magnitude
greater than the  comparable value to the calcium sulfate solution despite
Its high viscosity.  Maximum values were achieved by the passage  of one  pore
volume.
                                    4-64

-------
  i64-
1,5
CD
<
UJ
"S.
ce
UJ
Q_
  10^
  io7-
                                         ,OgO.
                                          LAB  MICA
                                          KEROSENE
                                          NONSATURATED
                                          GRADIENT 91


                                          •  REP I
                                          -X  REP 2
                                          O  REP3
                        PORE  VOLUME
 Source: Brawn, Thomas, and Green, 1984

    Figure 4-16. Hydraulic conductivity versus pore volume for laboratory compacted
          micaceous soil exposed to kerosene at a hydraulic gradient of 91.
                         4-65

-------
i
0>
CD
              u
              »
              in
              U
             -J

             CD
             <
             UJ
             2
             K.
                10"
                fo8
                                                                     O
                                  1.0
20
                                   LAB  MICA
                                   DIESEL FUEL

                                   NONSATURATED
                                   GRADIENT 91


                                 !  • REP I

                                 !  X REP 2
                                   O REP 3
                                   • REP 4
                                                    PORE
4.0
5.0
6.0
                      Source: Brown, Thomas, and Green, 1984
                                 Figure 4-17. Hydraulic conductivity versus pore voiume for iaboratory compacted
                                       micaceous soil exposed to diesel fuel at a hydraulic gradient of 91.

-------
   i66-
 >io7-
 03
 <
 UJ
 2
 tr
 LU
 Q_
   .68-
    I09-
LAB  MICA

PARAFFIN  OIL
NONSATURATED
GRADIENT  91


•  RER I
X R£f>2

O  REP 3
                        1 PORE  VOLUME 2
Source: Brown, Thomas, and Green, 1984


 Figure 4-18. Hydraulic conductivity versus pore volume for laboratory compacted mica-
          ceous soil exposed to paraffin oil at a hydraulic gradient of 91.
                              4-67

-------
   :66
  o
  03
  m
 >I07
 CD
 <
 LU
 5
 cr
 LU
 CL
   :68-
LAB  MICA

GASOLINE

NONSATURATED
GRADIENT 91
                                       RER 4
                       1 PORE  VOLUME 2
Source: Brown, Thomas, and Green, 1984

   Figure 4-19. Hydraulic conductivity versus pore volume for laboratory compacted
         micaceous soil exposed to gasoline at a hydraulic gradient of 91.
                                4-68

-------
  i6s
 o
 Q>
 m
>io7-
I-
 03
 <
 LJ
 2
 0=
 LU
 0.
   io9-
LAB  MICA
MOTOR  OIL
NONSATURATED
GRADIENT 91
                                X  RER 2
                        PORE  VOLUME2
Source: Brown, Thomas, and Green, 1984

   Figure 4-20. Hydraulic conductivity versus pore volume for laboratory compacted
         micaceous soil exposed to motor oil at a hydraulic gradient of 91.
                              4-69

-------
      Test  data  obtained with diesel fuel were variable and did not appear to
 Increase along  the  patterns of most organics tested.  No explanation is
 offered for  tfie unpredicted behavior.  Values were, however, greater by 1 to
 2  orders of  magnitude  than permeability to water.  This was also the case for
 gasoline.  The  test with motor oil showed a steady increase in perme-
 ability from 2  x 10~7  cm/s at 0.5 pore volume to 1.5 x 10~6 cm/s at 3
 pore  volumes.

 4.5.14.1   Discussion—
      The data obtained in tests with the commercial petroleum products
 illustrate the  importance of extended permeability tests to allow passage of
 several pore volumes of fluid.  Earlier data indicate that the effects of
 organic permeant fluids are retarded in tests where the samples are presatu-
 rated with water (or 0.01 N calcium sulfaite).  The tests on unsaturated
 samples may  serve as better estimators of maximum permeabilities that may
 result when  clay liners are exposed to petroleum products.

 4.5.15  Study by Brown and Thomas (1984) of the Permeability of
        Commercially Available Clays to Organics

      To determine the  effect of organic fluids on currently available clays
 that  are sold for sealing and lining impoundments, Brown and Thomas (1984)
 tested permeabilities  of three cpmmercial;ly available clays admixed with
 sand.

 4.5.15.1   Test  Method--
      Each  clay  was  mixed with sand to obtain a permeability to water of
 about 1 x  ID-8  cm/s.   Smectite is the dominant mineral in soil CC1 (blue
 bentonite) and  soil CC2 (a synthetically treated bentonite); a micaceous
 mineral is dominant in soil CC3 (Ranger Yellow).  The soils were compacted at
 optimum moisture in 10-cm fixed-wall molds using a mechanical  compactor as
 described  in ASTM Procedure 698-70.

     The compacted  soils were exposed to the test fluid without presatura-
 tion.  Following a  24-hour equilibrium period, a pressure of 15 psi (equi-
 valent to  a  hydraulic  gradient of 91) was applied to the liquid surface.
 Leachate passed through the samples was collected at intervals to allow
 calculation  of  the  soil permeability.  Fluids tested in replicate were water
 (0.01 N calcium sulfate), acetone, xylene, kerosene,-tiiesel fuel, gasoline,
 and used motor  oil.  A statistical analysis was performed to establish the
 variance among  the  data set for each permeant fluid.  Means were separated
 using a Duncan's  Multiple Range test at a significance level of P = 0.05.

 4.5.15.2  Test  Results—
     The test results  for all  permeant fluids are summarized in Table 4-12.
All of the organic  fluids tested produced dramatic increases over the cor-
 responding permeabilities to water, the increase ranging from 1 to 5 orders
 of magnitude.   Some of the increases, though large, were not statistically
 significant compared to the permeabilities measured with water due to the
 large variability seen 1n the tests.  The, increases in permeability were
 significant for all  clays permeated with xylene and for both the smectitic
clays when permeated by gasoline and kerosene.
                                    4-70

-------
 TABLE 4-12.  MEAN CONDUCTIVITY OF EACH SOIL TO EACH FLUID TESTED
                      (Brown and Thomas,, 1984)
Fluid
Water
Acetone
Xylene
Gasoline
Kerosene
Diesel fuel
Motor oil
CC1
3.61 x 10-8ba
5.05 x 10~5b
1.76 x 10-4a
1.96 x 10-4a
1.49 x 10-4a
5.17 x 10-5b
6.13 x 10-6b
CC2
2.58 x 10-8b
1.41 x 10-6b
7.28 x 10-4a
9.07 x~10-5a
9.10 x 10-5a
4.53 x 10-5ab
2.13 x 10-6b
CC3
1.57 x 10-8b
2.51 x 10-7b
1.00 x 10-4a
6.19 x 10~5b
5.68 x 10~5b
6.29 x 10-7b
9.48 x 10-7b
aValues in a given column followed by the same letter do not
 differ significantly (P = 0.05).
                               4-71

-------
     Generally the  increase  1n the micaceous clay permeability was less by 1
order of magnitude  than the  increases seen in the smectitic clays.  The
untreated bentonite (CC1) showed the greatest permeability increase in
response to each organic test fluid.  Since the untreated bentonite is the
soil that is most subject to shrinkage and the micaceous soil is least sub-
ject to shrinkage,  these findings are corisistent with the theory that shrink-
age resulting in greater spacing between peds is responsible for the changes
in soil permeability.

4.5.16  Studies Conducted for EPA by Daniel (1983) and Foreman and Daniel
        (1984) at the University of Texas, Austin

     Under a cooperative agreement with EPA, Daniel and others have carried
out research to address how  the permeability of clay soils is affected by
hydraulic gradient  and by the test device when the permeant fluid is other
than water.  Permeability tests were performed using three different types
of test devices—flexible-wall cells, fixed-wall compaction mold permeam-
eters, and consolidation cell permeameters—at hydraulic gradients of 10,
50, 100, and 300.   The three soils studied were a noncalcareous smectite
(Lufkin clay), a mixed-cation ill He (from Hoytville, Ohio), and a commer-
cially processed kaolinite (Hydrite R).  Fluids tested were water (actually
0.01 N calcium sulfate), methanol, and heptane (Foreman and Daniel, 1984).

4.5.16.1  Test Method-
     Most of the tests for the project were flexible-wall tests.  The fixed-
wall and consolidometer tests were performed to allow comparison of the data
from the different  devices.  Soil samples were compacted at or slightly dry
of optimum moisture content according to ASTM D-698.  Soils were scarified
between each lift.   Samples to be tested in flexible-wall cells were extruded
from the 10.2-cm (4-inch) -diameter compaction mold and trimmed to a height
of 9.4 cm (3.7 inches).  Similar diameter samples with a height of 11.9 cm
(4.7 inches) were tested in the fixed-wall permeameter setup.  Samples tested
in the consolidation cell were taken from the central portion of a compacted
10.2-cm (4-1nch) sample.  The sample v/as trimmed to a height of 1.90 cm (0.75
Inch) and a diameter of 6.4 cm (2.5 inches).

     Prior to the permeability measurements, the soil samples were saturated
with the permeant fluid to be tested.  For the flexibje-wall tests great care
was taken to completely saturate the samples.  This was accomplished through
soaking under vacuum and backpressuring.  During the permeability tests,
the backpressure was kept at about 2.8 kg/cm2 (40 psi) and the cell pres-
sure at 3.87 kg/cm2  (55 psi).  The average effective stress was 1.05 kg/cm2
(15 psi) for tests  at the .lower hydraulic gradients; an average effective
stress of 1.76 kg/cm2 (25 psi) was used when the gradient was 300.

 4.5.16.2  Test Results--
     Test results with Lufkin clay in the flexible-wall cells showed
essentially no change in permeability with time when methanol was used as the
permeant fluid.  Data were obtained for passage of about 0.9 pore volume.
The permeability to methanol  was virtually the same as with 0.01 N calcium
sulfate (Daniel, 1983).
                                    4-72

-------
       Methanol  test  results with  the  kaolinite show that when permeability is
 plotted  as  a  function  of  pore  volumes of flow, the curves have similar shapes
 for the  three types  of permeameters"V  The compaction mold yields somewhat
 higher permeability  results than  the  other two test devices.  Test data are
 shown  in Figure 4-21.

     Permeability  values  for the  kaolinite at different hydraulic gradients
 were obtained with water  and with methanol in the different test devices.
 The following conclusions were drawn:

     •  At  high hydraulic gradients (values of 150 or larger), kaolinite has
         a higher conductivity  to  methanol than to water regardless of
         permeameter  type.

     •  At  high hydraulic gradients,  the flexible-wall and consolidation-
         cell  permeameters yield similar hydraulic conductivities for both
         methanol and water; kaolinite is roughly twice as permeable to
         methanol as  to water for  these two types of permeameters.

     t  At  high gradients, use of compaction-mold permeameters leads to large
         sdatter in measured hydraulic conductivity.  On the average,
         compaction-mold devices showed kaolinite to be approximately 10 times
         more  permeable to methanol than to water.  The lowest values of K
         measured with the compaction-mold devices are nearly identical to
         values  measured with the  other two devices.  It is possible that
         sidewall leakage  contributed to the causes ....

     •   With  flexible-wall permeameters and two liquids and one soil, hydrau-
         lic gradient appears to have little effect on hydraulic conduc-
         tivity  . . . .

     •   With  consolidation-cell permeameters, hydraulic gradient has a very
         substantial effect on hydraulic conductivity.  At a hydraulic gradi-
         ent of  50, K to methanol  is only half of K to water, but at gradients
         of 200  to 300, K  to methanol is twice as large as K to water ....

     Figures  4-22, 4-23, and 4-24 show the effect of hydraulic gradient on
 tests with kaolinite in flexible-wall  cells,  consolidation cells, and fixed-
wall permeameters, respectively.  The scatter in the Tixed-wall  permeameter
data does not allow conclusions to be drawn although there appears to be a
trend  to  increased permeability with increased gradient.

4.5.17  Tests Conducted for Chemical Manufacturers Association by Daniel
        and Liljestrand (1984T

     In work  sponsored by the Chemical Manufacturers Association (CMA),
Daniel  and Liljestrand at the University of Texas at Austin carried out a
laboratory study of the permeability of five  clay soils to six aqueous fluids
representative of waste leachates or actual  liquid wastes.  The purpose of
the testing was to determine if dilute organic/water mixtures  produced the
increases in permeability demonstrated by other researchers using concen-
trated  organic liquids as permeant fluids.
                                    4-73

-------
  o
  O)
  U)

  E
  o
  >.


  >


  o
  3


  C
  o

 O


  o
 T3
  >s
            0
                      Pore    Volumes    of   Flow
Source: Foreman and Daniel, 1984


     Figure 4-21. Permeability versus number of pore volumes of flow for kaolinite
           permeated with methanol at a hydraulic gradient of 250 or 300.
                                4-74

-------
      -6
    0    h
u

-------
                                        ,20-0             300


                  Hydraulic;  Gradient

Source: Foreman and Daniel, 1984

           Figure 4-23. Permeability versus hydraulic gradient for kaoiinite
                 permeated in consolidation cell permeameters.
                          4-76

-------
        -6
 o
 o>
 en

 £
 o
 o
 3
-O
 C
 o
p

 u
T3
>^

X
        -7
     iO
      0
        -8
           0
                       M e t h a n o
                             100            200

                       Hydraulic   Gradient

Source: Foreman and Daniel, 1984

           Figure 4-24. Permeability versus hydraulic gradient for kaolinite
                       permeated in compaction moid cell.
300
                             4-77

-------
     The soils studied included Texas Lufkin clay (also used in tests  at
Texas ASM) and four soils supplied by CMA (identified as SI, S2, S3,, and  S4)
from actual landfill sites.  Properties of the clays are listed in Table
4-13.  Permeability tests were not performed on the SI clay since its  index
properties and mineralogy were similar to those of the S2 clay.

     Permeant liquids used in the tests were:  a leachate from a solid-waste
landfill (L2); two liquids (LI and L3) from industrial waste impoundments;  an
aqueous solution containing methanol at 5 percent (50,000 ppm); an aqueous
solution saturated with xylene (near 196 ppm); and the leachate, 11, spiked
with chloroform (200 ppm) and trichloroethylene (200 ppm) to simulate  a land-
fill leachate contaminated with chlorinated hydrocarbons.  Water used  to  pre-
pare the dilute methanol and xylene solutions was actually 0.01 N calcium
sulfate.  Characteristics of the leachates LI, L2, and L3 are listed in
Table 4-14.

4.5.17.1  Test Method--
     Permeability tests were carried out as described previously in Section
4.5.16.  All testing was performed usingiflexible-wall permeameters and
hydraulic gradients of 150 or 200.  Rates of flow were determined from the
rate of inflow for each test chamber.

4.5.17.2  Test Results—
     The permeability tests were performed for several months, allowing the
passage of more than one pore volume of fluid for most soil/leachate combi-
nations.  The permeabilities of the soils S2, S3, S4, and Lufkin clay  appear
to be related to the plasticity index, the permeability decreasing with
Increasing plasticity.  For any one soil, the permeabilities to the various
liquids were all about the same.  Permeabilities to the leachates did  not
differ significantly from the permeability to water (actually 0.01 N
calcium sulfate).  All permeabilities measured were 1 x 10~8 cm/s or
lower.  In three of the four soils tested, the permeability to 196 ppm xylene
was slightly lower than the permeability to the 5 percent methanol. All
permeabilities were plotted as a function of pore volumes of fluid passed
through the sample.

     In addition to the permeability tests, Atterberg limits of the soils
were determined using the various test fluids and pure xylene and methanol  in
place of water.  Test fluids LI, L2, L3, and spiked L-l did not significantly
alter the plasticity of any of the clay soils during the short-term exposure
of the test.  Mixing any of the five soils with pure xylene or pure methanol,
however, caused a drop in the liquid limit and destruction of the soil's
tendency to be plastic.  The dilute solutions of methanol and xylene (as  used
in the permeability tests) had much less significant effects on the plas-
ticity.  Only the soil S3 showed a large drop in plasticity when mixed with
the 5-percent methanol or the aqueous solution containing 196 ppm xylene.

     The significance of Daniel and Liljestrand's findings is that they
appear to show that dilute organic/water mixtures are not capable of causing
significant changes in the permeability of natural clay liners.
                                    4-78

-------
                      TABLE 4-13.  PROPERTIES OF CLAY SOILS TESTED BY  DANIELS AND  LILJESTRAND  (1984)
VI
to
Property
Natural water content (%)
Optimum water content (%)
Specific gravity
Percent finer than #200
sieve
Percent sand
Dominant minerals
Secondary minerals
Organic carbon content
(% of dry weight)
Cation exchange capacity
SI
23
17
2.73
93
7
Illite
Chlorite
1.46
10
S2
22
24
2.81
93
7
Chlorite
Smectite,
kaolinite
0.83
20
S3
47
31
2.71
94
6
Smectite
Kaolinite
1.39
40
S4
32
18
2.71
87
13
Quartz
kaolinite
1.79
5
Lufkin clay
	 i
23
21
2.66
81
19
Smectite
Kaolinite,
illite
0.28
25
            (meq/100 g)
          Plasticity index
21
32
59
16
                                                              42

-------
                   TABLE 4-14.  LEACHATE CHARACTERISTICS*
Parameter measured
or reported
Suspended solids (mg/L)
Dissolved solids (mg/L)
Volatile solids (mg/L)
Total organic carbon (TOC)
(mg/L)
Chemical oxygen demand (COD)
(mg/L)
Potential (ORP) (mV)
PH
Conductivity (jdnho/cm)
Metals (mg/L)
Cr
Cu
Pb
Ni
Zn
Organics (mg/L)
Ethyl benzene
Toluene
Nltrotoluene
Dinitrotoluene
Formaldehyde
Dichlorobenzene
Aniline
Toluenediamine

LI
465
20,202
5,768
1,440

2,160

398
6.9
23,700

1.0
5.3
0.36
0.18
6.0
b








Leachates
L2
162
1,043
121
13

12

268
7.1
865
b





b





*



L3
107
4,593
1,052
82
120
130

496
1.5
4,620
b






0.120
0.035
8
117
14
8
4
2
aData from Daniel and Liljestrand, 1984.
bNot reported.
                                    4-80

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 4.5.18  Study by Dunn (1983)  of the  Effects  of  Synthetic  Lead-Zinc Tailings
         Leachate on Clay Soils

     Dunn (1983)  evaluated the effects  of  a synthetic  lead-zinc tailings
 leachate,  of low pH and  containing large  concentrations of heavy metals, on
 the permeability of two  clay  soils.  The  permeability of  the clays was shown
 to be affected by the waste permeant,  with cation exchange and precipitation
 apparently being the most important  processes.

      The soils used in the testing,  Altamont soil and Rockville soil, had
 been identified  as potential  liner construction materials.  Altamont soil, a
 "valley  alluvium" with moderate plasticity,  is  a silty clay soil with 1 or 2
 percent  shale fragments.   Montmorillonite is the predominant clay mineral in
 Altamont soil.  Rockville soil,  a yellow-brown  silty  clay with high plas-
 ticity,  is composed of the fine fraction  from a sand  and gravel plant.  The
 predominant clay mineral  is kaolin.  This soil  probably contained micro-
 organisms  since  some evidence of bacterial growth was noted in soil that was
 stored for several  months.

      The permeant fluids  tested  were tap  water, distilled water, and the
 synthetic  lead-zinc tailings  leachate.  Characteristics of this-fluid were:

   .   t  Conductivity 1,550 ^mho/cm

      •  pH   = 2.6

      •  Lead  = 5.8-15.0 mg/L

      •  Zinc  = 200  mg/L.

 The  leachate  was  prepared with zinc sulfate, lead sulfate, and lead nitrate.
 Sulfuric acid was  used to attain the desired pH.

       Two  tests with  each clay were conducted with the synthetic leachate.
 Permeabilities obtained with  the test  fluid were compared to the results of
 samples  tested with  tap water and with distilled water.  All  the tests were
 run  at a compacted  dry density of about 90 percent of maximum dry density and
 at a water content  approximately 1 to 2 percent above optimum.  Tap water was
 used for the  molding water.  Soil samples were prepared with static compac-
 tion  since this method was found to be most appropriate for producing repli-
 cate  samples  at approximately the same dry density and water content.  The
 static compaction  involves compressing the soil  to a known density with
 applied  hydraulic  pressure.

      Tests were performed in a triaxial cell  at a hydraulic gradient of 50.
 Samples  tested were 3.81 cm (1.5 inches)  in diameter and 2.54 cm (1 inch)
 thick.   The samples were presaturated  (using a backpressure technique)  with
 the  fluid  to  be tested.  Prior to permeability testing, the samples were
 consolidated  at 1.5 kg/cm2 (21.3 psi) effective stress.  Permeability
measurements were carried out at an effective stress of 1.25  kg/cm2
 (17.8  psi).
                                    4-81

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     The permeability values measured in both soils exposed to the synthetic
 leachate were_higher than those measured with tap water.  Values measured
 with distilled water were lower than permeabilities measured with tap water.
 The ultimate effect of the synthetic leachate on the permeability to either
 soil could not be determined from the tests, however, because the perme-
 ability values did not reach steady state during the duration of the test
 (5,000 minutes or 3.5 days).  The tests with tap water did appear to reach
 steady state during this test time.

     For one Altamont sample, the measured permeability to the synthetic
 leachate was approximately 2 orders of magnitude higher than that of tap
 water.  This appeared to correlate with a long curing period (the period of
 time from compaction to the beginning of the permeability test).  Thixotropic
 alterations of the soil fabric may have occurred during this interval,
 resulting in the higher K value.

 4.5.19  Studies by Acar and Others (1984) on the Effect of Organics on
        Kaolinite

     In research funded by EPA, Acar, Olivieri, and Field (Acar et al., 1984b
 and c) and Acar, Hamidon, Field, and Scott (Acar et al., 1984a) studied the
 effect of four organic fluids on the saturated permeability of Georgia kaoli-
 nite.  The fluids tested—benzene, acetone, phenol, and nitrobenzene—were
 chosen because they represent a wide range of dielectric constants.  Compara-
 tive tests were performed with 0.01 N calcium sulfate.  In addition to the
 pure solvents, 0.1 percent (1,000 ppm) solutions of acetone and phenol pre-
 pared in 0.01 N calcium sulfate solutions were tested.  This research was
 carried out at Louisiana State University, Hazardous Waste Research Center.

 4.5.19.1  Test Method—
     The kaolinite was cured at 32 percent moisture for 1 week before compac-
 tion in a Harvard miniature mold at a compactive effort corresponding to
 standard Proctor compaction.  Sample dimensions were restricted to 3.55 cm in
 diameter and 3.8 to 5.1 cm in height.

      Tests were conducted in triaxial cells with continuous backpressure.
 Hydraulic gradients of less than 100 were used.  Backpressures of 414 to 449
 kPa (60 to 65 ps1) were used to fully saturate the samples prior to the per-
meability testing.  Approximately one pore volume of D.01 N calcium sulfate
was passed through the samples to establish the reference permeability
 value.  The Influent liquid was then switched to the organic fluid to be
 tested.  Tests were continued until the permeability readings and the efflu-
 ent concentrations were stable.

      A mercury Intrusion method was used to characterize the pore size dis-
 tribution in the samples before and after permeation with the organic test
 fluids and with the calcium sulfate (Acarlet al., 1984b).

      A fixed-wall test with acetone as well  as flexible-wall tests at vari-
able effective stresses were also carried out in order to evaluate the test
 scheme.
                                    4-82

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       Free-swell and liquid limit tests were conducted with the organic solu-
 tions and with the standard calcium sulfate to determine if these properties
 were affected by the chemicals.

  4.5.19.2  Test Results--
      All  tests with chemicals at low concentrations resulted in slight de-
 creases in permeability.  It was found, however,  that the chemicals  diffused
 through the flexible latex membrane so that the concentration of the organics
 that actually permeated the soil sample could not be ascertained.

       Reference permeabilities in all  kaolinite samples tested with  pure
 organics  were between 5.0 x ID"8 cm/s  and 6.0 x 10-° cm/s.   When pure
 organic fluids were introduced into the test cells, an immediate decrease
 in permeability occurred.  For acetone and phenol,  this decrease was followed
 by a permeability increase, the final  value stabilizing at  approximately
 double the initial  or reference value.  In the tests with benzene and nitro-
 benzene,  the permeability decreased until  the tests were terminated.  Final
 permeability values measured in these  tests were  2  orders of magnitude lower
 than the  reference  values.

      When acetone was tested in a fixed-wall  permeameter, the perme-
 ability stabilized  at 2 x 10-° while tests under  comparable conditions in
 flexible-wall  cells yielded values between 6 x 1Q-8 and 9 x lO"8.  The
 difference in  these test results is attributed to sidewall  leakage in the
 fixed-wall  test resulting from sample  shrinkage during permeation with
 acetone.   The  free-swell  tests also confirm that  shrinkage  would occur with
 acetone permeation.

      Both swelling  behavior and liquid limit  determined with  the specific
 pel-meant  fluid were found to relate to the changes  in  permeability measured.
 The  liquid  limit  and free swell  were increased  significantly with benzene and
 nitrobenzene,  slightly  increased with  phenol,  and decreased with acetone.

      Although  absolute  permeabilities  were altered  considerably  by permeation
 with  the  pure  organic fluids,  the mercury  intrusion  investigations showed
 that  the  size  and distribution  of pores greater than 80 A  were  not
 significantly  affected.   Since  pores with  diameters of  less than 80 A*
 are not expected  to  contribute  appreciably to the total flow, these  results
 suggest that physicochemical properties of  the pore fluid close to the clay
 surfaces  lead  to variations  in  flow  characteristics.

 4.5.20  Finding by Olivieri  (1984) of  Impermeability of Montmorillonite to
        Benzene'

     Olivieri  (1984) found  that benzene did not penetrate compacted Ca-
montmorillonite that was  first  fully saturated with 0.01 N calcium sulfate
 solution even at a hydraulic gradient as high as 150.  This finding was
attributed to hydraulic pressures being less than the required flow
 initiation pressure to two-phase  flow  (Acar and Seals, 1984).
                                    4-83

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4.5.21  Study of Permeability of Clays to Simulated Inorganic Textile
        Wastes by lulls (1983T!

     lulls (1983) tested Wyoming bentonite, Grolley kaoline, vermiculite,  and
White Store clay in compaction permeameters with alkaline metal  hydroxides.
Test solutions were ferrous hydroxide, cupric hydroxide, and manganese
hydroxide prepared from 1 N solutions of the respective sulfates by adding
sodium hydroxide until a precipitate formed.  The final solutions had pH
readings as follows:  ferrous = 12.9, manganese = 13.0, and cupric = 12.5.
Test results show an increase in permeability of the bentonite when it was
exposed to the alkaline permeant fluids.  The permeability of the kaoline
decreased with the application of the bases.  Neither the field clay nor the
vermiculite showed any significant variation in permeabilities with the test
fluid.

     Cracks observed in the bentonite indicate that shrinkage was the mech-
anism responsible for the observed increase in permeability.  The decreased
permeability of the kaoline was attributed to clogging of the pore space by
dispersed clay.  All of the leachates from the tests contained silica that
had been dissolved by the alkaline solutions.

4.5.22  Tests Conducted by Engineering Consulting Firms for Specific
        Application (unpublished data)

4.5.22.1  Tests Conducted by the Trinity Engineering Testing Corporation—
     The tests discussed below were performed by the Trinity Engineering
Testing Corporation at the request of the Corpus Christi, Texas, City Water
Department (White, 1976).

     4.5.22.1.1  Soil Characteristics and Test Method—A soil sample from a
proposed toxic waste landfill site was subjected to permeability testing with
isopropyl alcohol, benzene, and charcoal starter fluid.  The material tested
was a subsurface clay.  Composite samples: were compacted at optimum moisture
content to a height of approximately 91.4 cm (36 inches) at 95.8 percent
standard Proctor density in 2.54-cm (1-inch) inside diameter cylinders.  Each
of the three organic fluids was added to a level of approximately 61 cm (24
Inches) above the compacted soil samples.  Water was tested in a fourth
sample.  A constant pressure head of 7.01 m (23 feet^was Imposed with com-
pressed air.  Liquid level in each test cylinder was recorded every 4 hours
until all the liquid had penetrated the full 91.4-cm (36-inch) column of
compacted material.

     4.5.22.1.2  Test Results—In the experiments with Isopropyl alcohol and
water as the test fluid, the total drop 1n liquid level was less than 1 inch
over a 100-day period.  In the column tested with the charcoal starter fluid,
liquid began dripping from the bottom of the test cylinder after 122 days.
In the benzene test column, signs of full penetration throughout the clay
material were observed after 36 days.

     In a second experiment series, two 91.4-cm (36-inch) compacted clay soil
samples were tested with benzene.  The samples differed only 1n their mois-
ture content (sample A at 10 percent moisture and B at 20 percent moisture),.
Sample A showed signs of full penetration of the benzene after 20 hours.
                                    4-84

-------
 Full  penetration of benzene occurred after 32  days  in  sample  B,  and all
 liquid passed_ through the sample in  71  days.
                                  i* •      "'•?,•   ;
      The conclusions drawn from the  permeability  tests  are  stated below:

      •  Under optimum compaction,  the clays are highly  impermeable to
         domestic water and, conversely,  are very  permeable  to  lighter
         hydrocarbons.

      •  When  properly compacted to a finished  thickness of  91.4  cm (3 feet),
         the clays will  serve as a  suitable tank liner for domestic water but
         will  not contain  the lighter hydrocarbons.

      t  Under optimum compaction,  a  91.4-cm (3-foot) liner  of  the clay in a
         tank  7.01 m (23 feet)  deep containing  benzene can begin  to leak
         within  36 days.

      4.5.22.1.3  Discussion—Although the  soil sample used  in  the Trinity
 Engineering experiments is not adequately  characterized, the  results of the
 test  clearly  indicate potential  for  large  permeability  increases resulting
 from  exposure to concentrated  nonpolar  hydrocarbons.  The apparatus and test
 procedures used differ substantially from  those used in permeability tests
 conducted by  other investigators.

      The data also illustrate  the  importance of moisture content during com-
 paction. The performance of clay-soil  liner in contact with chemicals such
 as  benzene could be drastically influenced by  the uniformity of  the moisture
 content  when  the liner material  was  installed  and compacted.

 4.5.22.2 Test  Data Submitted  to Pennsylvania  Department of Environmental
          Resources—
      The Pennsylvania Department of  Environmental Resources has  received data
 pertinent to  clay liner/chemical compatibility.  The data pertain to specific
 sites  and specific wastes and  were submitted to the State by consulting engi-
 neers.   Testing  procedures vary and  information needed to evaluate the data
 is  not always provided  in the  reports.  All test results show the clay liner
 permeabilities  to be  "within the range required" after exposure to the wastes
 tested.
                                                     *
      Report A deals with  tests  to  evaluate  effects on a liner material  in
 contact  with  a waste  comprised  of  one part  oil  contaminated soil and four
 parts water.  For the permeability tests,  samples were air dried and then
 recompacted,  at  +2  percent of  optimum moisture content, to 95 percent of
maximum  dry density.  Stainless  steel molds 10.2 cm (4 inches) in diameter
and 11.7 cm (4.6  inches)  in height were used.   After trimming, the molded
 sample was transferred  to  a constant head permeability device.  A back-
pressure was  applied  to two of  the four samples during saturation with  0.01 N
calcium  sulfate  solution.  Permeability measurements with the calcium sulfate
showed no significant differences  between the  results for samples with  or
without backpressure.  Thus, it was concluded  that the effect of entrapped
air was minimal.

     After permeability tests with the standard calcium sulfate, the  liner
samples were placed in contact with the  test fluid,  sealed,  and placed  on a
                                    4-85

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 rocking table for 30 days.   Three  of  the  samples were tested with the waste
 fluid and one-with calcium  sulfate solution.  After 30 days, the samples were
 drained and the permeability tests repeated.  Reported results are shown in
 Table 4-15.

      No discernible .color change was  observed after a 30-day exposure to the
 waste fluid.   No shrinkage  along the  sides of the mold was observed, although
 a  change in height of approximately 0.64  cm  (0.25 inch) was reported.

      The waste tested—one  part oil contaminated soil and four parts water-
 was  not characterized further.  Neither the extent of the oil contamination
 nor  the characteristics  of  the contaminated oil were reported.  It may be
 assumed that  either tap  water or deionized water was used to prepare the
 waste fluid.   The extent to which  the oil or its contaminants would be
 extracted by  the water is unknown  but probably very small.  Although it is
 not  discussed in the  report,  the waste material in contact with the clay
 liner sample  may have involved three  phases, with oil being the lightest
 phase.

      No indication of the length of the permeability testing procedure or
 pore volumes  displaced is given.   The hydraulic heads used in the tests also
 are  not reported.   These details may be stated in a letter that is referenced
 in the  report.   Soil  characterization data were not included.

      Report B describes  the results of a similar investigation in which liner
 samples  from  a  disposal  site were  tested with four different wastes.  The
 permeabilities  are reported in Table 4-16.  All samples showed slight (two-
 fold)  increases  in permeability after a 30-day exposure to the wastes.  It
 is notable  that  "control  sets" exposed for 30 days to 0.01 N CaS04
 showed  similar  increases.

      Soil properties  are  listed below:

      Cation exchange  capacity:  11.1 meq/100 g soil
      Predominant exchangeable cation:  Calcium
      Major mineral  fraction:  Alpha quartz
      Other minerals  (trace  to minor):  Microcline, Adularia, Muscovite,
                                       Kaolinite
      Percent  clay  size (  0.002 mm):  13
      Percent  silt  size (0.002 mm -0.05 mm): 30
      Percent  sand  size (0.05 mm -2.0 mm):  22
      Percent  larger than  2.0 mm:  35
      Liquid limit  (percent water):   31
      Plastic  limit  (percent water): 22

     Wastes used in the  tests were not characterized beyond the description
given in the  table.   Presumably, they were diluted with water as was done in
Case A, but this is not  stated in the report.  The duration of the tests,
pore volumes  replaced, and  hydraulic head are not provided in the report.

     Report C provides permeability data on a soil  sample tested with chrome
ore  leachate.  The leachate (pH = 13.0)  contained 1,400 mg/L total  chromium
and  1,200 mg/L hexavalent chromium.  A constant head test, conducted at a
pressure of 20 psi, gave a permeability of 1.2 x 10~8 cm/s.   With the
falling head method, a permeability of 2.2 x 1Q-8 cm/s  was measured.
                                   4-86

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             TABLE 4-15.  PERMEABILITY TEST RESULTS*
                       (Pennsylvania Case A)
Sample
AC
BC
C
D

With
1
5
9
1

0
.1
.9
.4
.7

.01
X
X
X
X
Coefficient
N CaS04
10-7
10-8
10-8
10-7
of permeabili
ty
After exposure
1.2
3.9
1.1
Not
X
X
X
(cm/s)
to test
10-7d
10-8
10-7

fluidb



tested
aTest data reported to Pennsylvania Department of Environmental
 Resources.


bTest fluid was one part oil-contaminated soil to four parts  water,

cSamples under backpressure during initial  permeability tests.

dControl sample—tested after 30-day exposure to  0.01  N CaS04«
                             4-87

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               TABLE 4-16.  PERMEABILITY TEST RESULTSa
                        (Pennsylvania Case B)
Coefficient of permeabil
Sample
A
B
C
Before exposure
to waste
1.4 x 10-8
1.4 x lO-8
1.8 x ID'8
After exposure
to waste
2.0 x 10-8
2.1 x 10-8
3.0 x 10-8
ity (cm/s)
Waste
Electric furnace
baghouse dust
Tar decanter sludge
(high in organics)
Neutralized pickle
                                               liquor rinse water
                                               sludge

  D         1.8 x 10-8         3.0 x 10-8      Hot strip mill recycle
                                               system sludge (high in
                                               oil)


aTest data reported to Pennsylvania Department of Environmental
 Resources.
                                4-88

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      Soil characterization and details of the test method were not provided
 in the brief_report.

 4o5.22.3  Studies Sponsored by Waste Management,  Inc.—
      Waste Management, Inc., has sponsored a series of studies to  determine
 compatibility between landfill leachate and in situ clay soil, which  func-
 tions as the landfill liner.  (Weaver and Brissette,  Canonie  Environmental
 Services Corporation, 1982).  Permeability data were  obtained in triaxial
 devices.  Each report includes details of the sampling effort, soil char-
 acterization data, and the permeability test results. One important  con-
 clusion by Canonie is as follows:

      ... It has been our experience that in concentrations  of less  than 1
      percent organics have no significant impact  on soil  permeability.

      The laboratory permeability results  presented in each of the  reports
 indicate that no appreciable change  in permeability will  occur on  soils at
 the specific sites due to contact with the waste  leachate obtained from the
 facility.

 4.5.22.4  Test Data from D'Appolonia Consulting Engineers,  Inc.—
      D'Appolonia Consulting Engineers, Inc.  (D'Appolonia),  has performed
 numerous permeability studies involving  site-specific soil  samples and
 leachates.  Projects have involved slurry trench walls as well  as  liners for
 landfills.  In 1983 D'Appolonia  compiled  their permeability test data from
 14 projects  (D'Appolonia Consulting  Engineers,  Inc.,  1983).   Leachates
 tested  in the D'Appolonia projects were  frequently high  in  salts,  and some
 were  highly  acidic.  All  data were obtained  from triaxial  tests.   Perme-
 ability data from the various projects are summarized below.

      Project A—No significant changes were  observed  in  long-term  perme-
 ability tests  on soil  samples containing  2 percent or 3  percent commercial
 bentonite when they were subjected to  an  aqueous waste fluid  of pH  7.  The
 fluid,  collected during  dredging operations  and shipped  to  D'Appolonia by
 the client,  contained minor concentrations  of  a number of inorganic salts
 (sulfate,  chloride,  fluoride).  Specific  conductance  was  reported  as 1,710
 /^mho/cm.

      The  permeability tests  involved the  exchange  of"up  to 4.7 pore volumes
 with  test  times  of 24 to  76  days.  The hydraulic gradients used varied
 from  36  to 168;  cell  pressures were  1.0 to 1.5 kg/cm2.

      Project B—Extensive permeability tests were performed on reddish-brown
 clay  samples  (undisturbed Shelby tube  samples) using a stabilized pH 4
 fluid.  The  fluid was  prepared in the  laboratory using pond water and waste
 from  the site.  The most  significant characteristic of the stabilized
 pH 4  fluid was the  specific  conductance at 94,000 //mho/cm at 25° C; pH was
 3.88.  It should be noted that Shelby tube samples may not always  be com-
 pacted to exactly the  same density so that slight deviations in measured
 permeability are not considered to be significant.

     Although all permeabilities measured were below 1 x  10~7  cm/s, a
trend toward increased permeability was apparent as more  pore  volumes  were
exchanged.  Changes in soil chracterization were also  in  evidence as more
                                    4-89

-------
 pore  volumes  of  test  permeant fluid were passed through the samples.
 Elevated  hydpaulic gradients 110 and 450;were used for the tests, and
 cell  pressures were 2.5 and 4.5 kg/cm2.  Test times ranged from 100 to
 350 days.   In three of the samples, more1than 12 pore volumes were
 exchanged.                               !

      Project  C—- A waste fluid characterized by high salt concentration and
 high  total  organic carbon was tested in four soil samples.  The samples
 contained varying proportions of two soils—a fine-to-coarse sand, and a
 sandy clay  with  1 to  3 percent commercial bentonite.

      Permeability tests were run at a hydraulic gradient of 20.  After ini-
 tial  permeability increases in some samples, the permeabilities decreased.
 Samples were  tested for 692 days.  For each sample, between 2 and 13 pore
 volumes were  exchanged.  The permeability decrease noted was approximately 1
 order of magnitude for a cement bentonite sample.  For the other three soil
 mixtures, permeability decreased by a factor of 2 to 4.

      The  constituents present in the permeant are not known precisely.
 Available chemical analysis data indicate that the chemical concentrations
 1n the waste  material vary considerably from year to year.

      Project  D—Slight decreases in permeability were reported for clay-soil
 samples (with bentonite) exposed to contaminated groundwater samples taken
 from  piezometers.  Soil samples were 25 percent flyash, 25 percent uncon-
 taminated clay, 25 percent contaminated clay, and 25 percent silt.
 Bentonite (1  percent) was added.

      Two permeant fluids were tested; pH values were 10.57 (Sample A) and 8.8
 (Sample B).   Specific conductance was reported at 35,300 and 13,200 ymho/cm
 at 25°C.                                 :

      Samples  were tested at a gradient of 190 with cell pressure at 1.5
 kg/cm2.  Test duration was 90 days with more than three pore volumes
 exchanged.  Final permeabilities were determined to be below 1 x 10~8
 cm/s.

      Project  E—Permeability tests were run on a silky clay soil from a pro-
 posed  facility with four waste leachates as the permeant fluid.  Soil
 samples were  compacted in the laboratory (95 percent of standard Proctor
 density).   Chemical characteristics of the waste fluids tested are shown in
 Table  4-17.

     Permeability tests were performed at a hydraulic gradient of 47 and
 cell pressure of 0.75 kg/cm2.  Total  test time was 40 to 50 days.  The
 results of  the permeability tests are given in Table 4-18.  All samples were
 saturated with 0.01 N calcium sulfate solution prior to introduction of the
waste  fluid.

     Project  F—Permeability data on undisturbed Shelby tube samples
 tested with tap water showed permeability values ranging from 6.1 x 10~8
 to 2.0 x 10~9 cm/s with an average of 1.0 x 10~8 cm/s.  Fifty-seven
 samples were tested with total  test time varying from 6 to 10 days.
 Hydraulic gradient was 25 to 50, and cell pressure was 3.5 to 5.5 kg/cm2.
                                    4-90

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     TABLE 4-17.  CHEMICAL CHARACTERISTICS OF WASTE PERMEANTS, PROJECT E*
Waste leachate permeant fluid0
Parameter
Column test designation
Ph
Specific conductance

Filterable residue at
180 °C
Acidity
Alkalinity
Phenolpthalein
alkalinity
Chloride
Sulfate
Dissolved metals:
Cadmi urn
Calcium
Chromium (hexavalent)
Chromium (total)
Iron
Lead
Magnesium
Manganese
Nickel
Selenium
Sodium
Zinc
Units

pH units
^mho/cm
'at 25°C
mg/L

mg/L CaCOs
mg/L CaC03
mg/L CaCOs

mg/L
mg/L

mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
No. 3
P-l
12.63
20,500

12,100

0
4,140
2,660

1,600
50

0.02
610
450
880
<0.1
0.49
<0.1
0.07
0.23
1.86
945
3.82
No. 4
P-2
11.23
11,900

8,620

0
130
90

2,300
2,550

<0.01
170
14
16
<0.1
0.32
0.4
0.04
0.10
0.196
1,860
0.12
Sludge
P-3
8.37
10,100

8,720

0
20
2

570
500
-
<0.01
1,800
0.06
0.08

<0.6l
135
0.14
.0.46
<0.001
12
0.02
Composite
leachate
P-4
11.23
11,000

8,380

0
224
143

1,800
2,250

<0.01
505
21
52

0.01
2.8
0.06
0.10
0.342
1,350
0.03
aData from D'Appolonia Consulting Engineers,  1983.

DLeachates were generated from various wastes by 1:4  shake  extraction of
 solid waste with water.

Composite leachate obtained by mixing four waste leachates in the following
 proportion:

   No. 3 leachate  - 5 percent
   No. 4 leachate  - 75 percent
   No. 5 leachate  - 5 percent (composition not  specified)
   Sludge leachate - 15 percent.
                                   4-91

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    TABLE 4-18.  RESULTS OF PERMEABILITY TESTS, PROJECT Ea
Sample
fluid
P-l
P-2
P-3
P-4
Permeant
0.01 N CaS04
No. 3 leachate
0.01 N CaS04
No. 4 leachate
0.01 N CaS04
Sludge leachate .
0.01 N CaS04
Composite leachate
Pore volumes
exchanged
0
3.2
0
0
4.7
13.5
0
0.8
- 3.2
- 12.7
- 8.8
- 4.7
- 13.5
- 17.2
- 0.8
- 5.6
Permeability
(cm/s)
1.6 x ID'7
1.7 x ID-7
1.4 x ID'7
1.1 x 10-7
1.3 x 10-7
1.4 x 10-7
1.5 x 10-7
2.4 x 10-7
4.2 x 10-7
1.1 x 10-7
1.2 x 10-7
8.1 x 10-7
aData from D'Appolonia Consulting Engineers, Inc., 1983.
                             4-92

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      Project G—Slurry wall  test data were provided for two different
 leachates  identified as  low  pH or high pH.  A commercial bentonite product
 was added  to a  elay-sand mix.  Sixty-day tests at hydraulic gradients of
 170 to 205 and  cell pressure at 1.5 kg/cm2 gave permeability values below
 7 x 10~8 cm/s.  Between  19 and 47 pore volumes were exchanged in the
 tests.

      Project H--Potential clay liner materials were tested with a permeant
 fluid generated in the laboratory by leaching a young slag from a pilot
 plant.  The pH  of the leachate was 4.90; specific conductance was 2.70
 jumho/cm at 25°C.

     Hydraulic gradients of 25 and 100 and cell pressures of 0.75 and
 1.5 kg/cm2 were used in the permeability tests.  Distilled water was
 used to saturate the samples.  Small permeability decreases were observed in
 tests with the  slag leachate.  Total testing time was approximately 2 to 3
months.

     Project I—Groundwater spiked with several chlorinated hydrocarbons was
 used as the permeant fluid in tests on undisturbed Shelby tubes samples.
The total  concentration of chlorinated ethanes was 500 ppm.  The soil sam-
ples tested were comprised of smectite (50 to 75 percent), kaolinite (10 to
25 percent), vermiculite (10 to 25 percent), mica (10 to 25 percent), and
quartz (10 to 25 percent).

     Permeability tests were conducted at a hydraulic gradient of 150 and
a cell pressure of 1.5 kg/cm2.  Four samples were tested for up to 140
days with  a maximum of 24 pore volumes exchanged.  Distilled water was used
as the initial permeant fluid.  Slight decreases in permeability were
observed with the spiked groundwater as permeant fluid.

      Project J—Two soil samples were tested with a highly acidic waste
fluid (pH  = 1.5) that was collected from waste ponds.  Other significant
characteristics of the fluid were specific conductance = 22,200 ^mho/cm at
25°C and sulfate = 15,000 ppm.

     Slight decreases in permeability were observed after exchange of more
than 10 pore volumes.  Hydraulic gradients of 20 to U)0 were used with
cell pressures of 0.7 to 2.0 kg/cm2.

     Project K—Three waste fluids were tested with a sandy soil  mixed with
a commerical  bentonite product.  Significant characteristics of the waste
fluids are shown below.

            Parameter             	Waste fluids	

                pH                  8              9           10
                °K                  6.65            7.65         5.00
       Specific conductance       920          1,000          430
         (jumho/cm at  25°C)
          Sulfate (ppm)            470            460          180
                                    4-93

-------
     No  significant  change  in permeability occurred when the pH 9 fluid was
 tested with  the  sandy  clay  soil.  The test involved exchange of 7.4 pore
 volumes.  A  slight increase in permeability was noted with the pH 8 fluid
 tested with  the  sandy  clay  soil after 4.7 pore volumes were exchanged.  Waste
 fluid at pH  10 tested  with  the sandy clay soil mixed with bentonite decreased
 permeability after exchange of 4.2 pore volumes.

     A hydraulic gradient of 22 was used for the tests involving the waste
 fluids and soil.  A  hydraulic gradient of 100 was imposed on the soil
 bentonite tested with  pH 10 fluid.  Cell 'pressure was 1.1 kg/cm2.  The
 pH 8 and 9 samples were tested at a hydraulic gradient of 22 and a cell
 pressure of  1.0  kg/cm2.

     Project L—- Two waste fluids with neutral pH were used in tests with soil
 mixed with approximately 1  percent treated bentonite from three vendors.  The
 only notable characteristic of the waste fluids was specific conductance.
 The permeability data  are summarized in Table 4-19.  The hydraulic gradi-
 ent used in  the tests  was 80 to 90; cell pressure was 1.0 kg/cm2.

     Project M—Permeability tests were performed on 20 soil samples to
 determine the effect of a permeant fluid of pH 1.5.  The fluid, collected
 from waste ponds at a  disposal site, had a high salt concentration
 (specific conductance  = 22,200 jumho cm at 25°C; sulfate = 15,000 ppm).

     The only permeability  Increases noted were for a soil  characterized as
 silt stone and one characterized as sand !stone.  For these samples, perme-
 ability increases were just  less than 1 order of magnitude after passage of
 approximately 12 pore  volumes.  Hydraulic gradients used in the tests
were 15 to 285; cell  pressures were Oo75 to 4.00 kg/cm2.

     Project N—Permeability studies on three composite soil samples were
 conducted.   Three waste leachates used as the permeant fluid were prepared in
 the laboratory by extracting tailings from a pilot plant.  Fluids tested were
 characterized by pH  (3, 6,  or 9).

     Initial permeabilities were determined with groundwater from the pro-
 posed site.  The results of the permeability tests are shown in Table 4-20.
 Permeability increases of approximately 1 order of magnitude were observed in
 the glacial  till  samples tested with permeant fluids of pH 6 and 9.

 4.5.23  Tests Reported by  Bentonite Companies

 4.5.23.1  American Colloid Company—    ;         .
     The American Colloid Company produces Volclay®soil sealants.  These pro-
ducts are a  special type of high swelling sodium montmorillonite that has
been treated by a proprietary process to render the material unreactive
toward most chemical  materials.  American Colloid Saline Seal  100®is a
patented product Intended for use in containing wastes with high levels of
dissolved salts,  acids, or alkali.
                                    4-94

-------
            TABLE 4-19.  RESULTS fOF PERMEABILITY TESTS, PROJECT La
-
Waste fluid
(1,900 wmho/cm
A
at 25°C)
Pore volumes
K-max/Mnitial replaced
Cement
bentonite
Aqua gel
Saline seal
1.0
2.2
•1.6
6
8
7
Waste fluid B
(3,800 /amho/cm at 25°C)
Pore volumes
fynax' ^initial replaced
1.0 13
6.9 7
3.9 13
 aData from D'Appolonia Consulting Engineers,  Inc.,  1983.
          TABLE 4-20.   INITIAL AND  FINAL  PERMEABILITIES  DETERMINED  IN
                TRIAXIAL CELL  TESTS WITH  LEACHATES,  PROJECT  Na
Sediment sample
Glacial till
(Composite No. 1)
Stratified drife
(Composite No. 2)
47. Bentonite/till
Admixture
Leachate
permeant
PH
3
6
9
9
3
6
9
9
3
9
Laboratory permeability @ 20ob
(cm/s)
initial with
site groundwater
5.5 x 10-8
3.8 x 10-8
5.7 x 10-8
3.6 x 10-7
1.8 X 10-5
1.5 x 10-5 ^
1.3 x 10-5
2.1 x 10-5
1.0 x 10"10
1.0 x 10'10
Final with
waste leachates
1.4 x 10-7
3.4 x 10-7
5.6 x 10-7
5.7 x 10-7
1.3 x 10-5
1.2 x lO-5
1.3 x 10-5
2.1 x 10-5
1.5 x 1010C
1.5 x 10-10d
aData from D'Appolonia Consulting Engineers, Inc., 1983.

bPermeability calculations based on final column sample dimensions.


cDetermined as 83.1 percent saturation based upon final moisture content
 measurements.


dDetermined as 83.4 percent saturation based upon final moisture content
 measurements.
                                  4-95

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     American Colloid has conducted permeability tests of Saline Seal  100
with gasoline-, kerosene, and 1,1,2-trichToroethane.  The trichloroethane
tested was waste solvent that had been contaminated with other unchar-
acterlzed materials.  It was said to be predominantly trichloroethane
(Jepsen, 1983).

     The American Colloid tests were conducted with a fixed-wall compaction
permeameter.  Inside walls of the cylinder were coated with a thin film of
slurry to provide a barrier against capillary effects along the wall.
Samples were compacted to at least 90 percent Proctor.  Soil samples were
either 5.1 or 10.2 cm (2- or 4-inch) -thick cores and consisted of a uniform
standard silica sand mixed with between 6 and 15 percent bentonite (dry
weight).  Test samples were prehydrated with deionized water for at least  48
hours, and provision was made for deairing.  After the test fluid was  added
to the permeameter, head loss was recorded periodically until stable read-
ings were established.  The results of these permeability tests are shown  in
Table 4-21.

 4.5.23.2  Federal Bentonite--
     Another major bentonite company, Federal Bentonite, produces, among
other bentonite products, petroleum tank farm sealants.  The products  are
made by treating sodium-bentonite with specific polymers in order to obtain
the desired sealing characteristics.  PPS-21 is a free-flowing granular
bentonite product designed to promote an impermeable barrier in the event  of
failure or leak In petroleum tank farms.;

     Permeability tests with water and with kerosene were performed on 5.1 cm
(2-1nch) samples of test soil consisting of PPS-21 mixed with washed beach
sand.  Samples were prehydrated with deionized water under a 136-cm head
prior to introduction of the kerosene.  Tests results are summarized in
Table 4-22.

4.5.23.3  Discussion—
     The behavior of polymer-treated bentonites over a long time period is
not demonstrated in the test results presented here.  Although the duration
of the American Colloid tests exceeded 40 days, only a fraction of a pore
volume of fluid was displaced during the tests.  The number of pore volumes
was not expressed in the data presented by Federal Bejitonite.

     Suggestions that the polymers in the treated bentonites will degrade
after 3 to 4 years have been made, and at least two laboratories claim to
have data 1n support of this time-degradation behavior (Seattle, 1983;
Zlamal, 1983).  Many applications for the treated bentonites involve short-
term performance requirements.  In long-term applications, such as barriers
for landfills', the time-degradation issue could have serious implications.
The long-term viability of treated bentonite seals needs to be verified.
                                    4-96

-------
               TABLE 4-21.  EFFECT OF CONCENTRATED ORGANICS  ON A
                            TREATED BENTONITE SEAL3
Test duration
Organic permeant (days)b
Gasoline 68
Kerosene 40.2
1,1,2-Trichloroethane 71
(waste)
Pore volumes Permeability
displaced (cm/s)
0.6 4.7 x 10-7
0.16 4.7 x 10-8
0.58 4.2 x 10~7C
 Unpublished data  on  Saline  Seal  100® from American Colloid Company,
  personal  communication,  January  23,  1983.

 bAll  tests conducted  using a hydraulic head of 76.2 cm  (2.5 feet).

 Permeability of prehydrated soil was  1.5 x 10~7 cm/s prior to
  addition  of organic  permeant.
        TABLE 4-22.  PERMEABILITY  (cm/s) OF A TREATED BENTONITE SEAL
                               TO  KEROSENE3»b

Sample
Sample 1:
(Prehydrated for
Sample 2:
(Prehydrated for
Sample 3:
(Prehydrated for
Sample 4:
(Prehydrated for


24 h)

48 h)

72 h)
96 h)
Prior to
addition
of kerosene
5.1 x 10-8
3.2 x 10-8

2.0 x ID'8

1,3 x 10-8
After exposure
to kerosene
for 7 days
3.4 x 10-8
2.2 x 20-8

1.3 x 10-8

1.1 x 10-8
After exposure
to kerosene
for 42 days
2.5 x 10-8
1.5 x ID"8

1.6 x 10-8

9.6 x 10-9
3Data from Federal Bentonite (1983) on tank farm sealant PPS-21.

bTests conducted under a standard 136-cm head using  a falling  head
 permeameter.
                                   4-97

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4.6  REFERENCES

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Acar, Y. B., A. Hamidon, S. Field, and L.;Scott.  1984a.   Organic  Leachate
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Acar, Y. B., and S. D. Field.  1982.  Organic Leachate  Effects  to  Hydraulic
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Anderson, D. C. 1981.  Organic Leachate Effects on the  Permeability  of  Clay
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Anderson, D. C., 1982.  Does Landfill Leachate Make Clay  Liners More
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Bowders, J. J., D. E. Daniel, G. P. Broderick,  and H. M.  Llljestrand.  1986.
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                                    4-99

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Daniel, D. E. 1983.  Third Quarterly Progress Report to the U.S.  EPA for  the
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                                    4-100

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                                    4-102

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van Schaik, J. C., and G. E. Laliberte.  1968.  Soil Hydraulic Properties
    Affected by Saturation Technique.  Canadian Journal of Soil Science.
    49:95-102-.

Weaver, J. W., and R. F. Brissette.  1982.  Personal communication with Waste
    Management, Inc., three reports.  A, B, and C.

Weiss, A. 158.  Interlamellar Swelling as a General  Model  of Swelling
    Behavior.  Chem. Ber. 91:487-502.

White, R. 1976.  The Permeability of a Clay Material Taken from a Proposed
    Toxic Waste Landfill Site as Affected by Different Liquids.  Personal
    communication from Trinity Engineering Testing Corp.  to the City of
    Corpus Christi, Texas.

Yong, R. N., and B. P. Warkentin.  1975.  Soil  Properties  and Behavior.
    Elsevier Scientific Publishing. Company, New York.

Zimmie, T. F., J. S. Doynow, and J. T. Warden.  1981.  Permeability Testing
    of Soils for Hazardous Waste Disposal Sites.  In:  Proceedings of the
    Tenth International  Conference on Soil  Mechanics and  Foundation Testing,
    Vol. 2.  Stockholm,  Sweden, pp. 403-406.

Zlamal, F.  1983.  Slurry Systems Contractors and Consultants,  Gary, Indiana,
    Personal communication with Research Triangle Institute.

Zoeller, A. 1982.  Review of Texas A&M University Studies  on Clay Soils and
    Organic Reagents.  Commonwealth Edison, Chicago.  Appendix  C to Comments
    of Utility Solid Waste Activities Group, The Edison Electric Institute
    and The National  Rural  Electric Cooperative Association on  Sections 3004
    and 3005 of the Resource Conservation and Recovery Act of 1976:
    Permitting Standards for Land Disposal  Facilities.
                                   4-103

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                                  CHAPTER 5

            CURRENT  PRACTICES:  CLAY LINER DESIGN AND INSTALLATION


      This  chapter describes  the  state-of-the-art knowledge and techniques
 currently  used  for  clay  liner design and installation.  Information in this
 chapter was compiled  from a  variety of sources, including a review of exist-
 ing  literature  on design and installation for various applications and inter-
 views with  key  personnel from selected engineering firms, waste management
 companies,  government agencies,  professional associations, and contractors,
 all  of whom are experienced  in various aspects of clay liner installation and
 construction.   The  number of clay-lined facilities designed specifically for
 hazardous waste containment  and  information on these sites are somewhat
 limited.   In addition, the design and installation practices for clay liners
 for  other applications are similar to those for hazardous waste facilities
 (though possibly not  as  rigorous in design and installation procedures).  For
 these reasons,  information from  these applications is included as well.

      Clay  liner construction utilizes equipment and techniques similar to
 those used  in other earthwork construction projects.  However, the soil
 compaction  practices  used to achieve low permeability employed in clay liner
 construction differ from compaction practices used for strength and stabil-
 ity,  as used in foundations and  roadbeds.  For cohesive soils (i.e., clays),
maximum strength is achieved when soil is compacted at dry of optimum
moisture content (see Chapter 3 for a discussion of compaction parameters),
but  the lowest  permeability  is achieved 2 to, 3 percent wet of optimum
moisture content.  Therefore, when clay liners are compacted, it is necessary
to specify  and  control carefully compactive effort, density,  and moisture
content to  ensure that the desired permeability is achieved.

     The first two sections of this chapter describe current  practices for
designing and constructing clay liners.  Literature reviews and interviews
with design engineers and contractors indicate that construction quality
assurance (CQA) and construction quality control  (CQC)  are considered among
the most important elements of successful  facility construction, with clay
liner failures often attributed to deficiencies in these areas.  Because of
the  importance of CQA and CQC activities during the construction of clay
liners, this subject is covered separately in the third section of this
chapter, including a description of the element of a CQA plan.  Common
problems encountered during clay liner construction and solutions to these
problems are tabulated in the final  section of this chapter.

5.1  DESIGN

     The fundamental aspects that must be considered during the design of a
clay liner are:

       t  Stability of the liner against major earth movements such as
          slope failure,  settlement,  and bottom heave


                                     5-1

-------
        •  Resistance of the liner to fluid  flow  (I.e., permeability)

        •  Compatibility of the liner material with  the wastes  1t 1s
           meant-to contain

        •  Long-term durability of the liner.

 The design effort applies standard geotechnical  engineering practices to
 address these considerations and thus to meet the special performance
 requirements of clay liners.

      Clay liner design is very site and material specific.  Waste volume
 requirements and waste characteristics must be considered during the design
 effort, and facility designs must be tailored to the  site-specific condi-
 tions.   The design effort may be divided into the following activities:

        •  Site investigation

        •  Liner material  selection and characterization

        t  Facility design

        •  Preparation of  construction specifications  and the quality
           assurance (QA)  plan.

 Site investigation, liner material  selection, and Uner material characteri-
 zation  are done prior to  facility design.   Preparation of construction
 specifications and the QA plan  follow facility design.  Most of the design
 engineers  interviewed during the course of  this  project emphasized that
 design  activities  usually continue through  the construction of the clay liner
 because unexpected situations often  arisfe that necessitate modifications in
 the  original  plans.

 5.1.1   Site  Investigation

     As with  any earthwork project,  a  clay-lined hazardous waste containment
 facility must be designed to be  compatible with  the geological  conditions at
 the  specific  site.   For this reason,  the first step in the design effort is a
 comprehensive evaluation  of  the  site.  Ideally,  sites should be selected
 according  to  the suitability of  the  in situ earth materials for containing
 hazardous wastes.   However,  in actual  practice this is not always possible-
 Constraints  such as land  use, zoning  laws,  land ownership, and distance to
 waste generators often  result in  sites being selected for reasons other than
 their technical suitability  for  containing wastes.  This fact,  combined with
 the  subsurface  heterogeneity and  spatial  variability that is the rule 1n most
 geologic environments, makes adequate  site  investigation a critical  part of
 facility design.

 5.1.1.1  Purpose—
     Site  investigations  are conducted to delineate a site's topography, sub-
 surface geology, and  hydrogeology.  Topography influences facility configura-
 tion and drainage  system  design  (runon/runoff control).  Subsurface site
 Investigations are  necessary to determine whether soils suitable for liner
material are  available at the facility site or whether it is necessary to
                                     5-2

-------
 identify  and  investigate borrow sources.  In addition, knowledge of in situ
 soil  properties  is  important for foundation design.  Soil characteristics
 influence seTection of the method of slope stability analysis appropriate for
 facility  destpr are a necessary input to stability analyses, and determine
 the necessity for special design measures to control settlement or to ensure
 maximum protection against contaminant migration.

      Hydrogeologic  information about the site is important for the proper
 monitoring of well placement.  From a design standpoint, it is important to
 determine the depth to water table for the site, including seasonal variabil-
 ity.  Some States require a specific thickness of unsaturated soil between
 the facility  base and the water table.  For sites with high water tables,
 this  can  necessitate aboveground facility design.  In States where facilities
 can extend below the water table, high groundwater levels can necessitate
 special intergradient (below water table) designs.  Groundwater elevations
 are necessary for assessing liquefaction potential for in situ soils where
 significant seismic ground motion .can occur.  Hydrogeologic investigations
 also are  necessary to locate, identify, and delineate hydrologic pathways
 (e.g., fractures and sand seams) at the site so that provisions for sealing
 them can  be incorporated into the facility design.  These pathways can con-
 tribute to rapid migration of wastes from the facility if a liner leak
 occurs.   In addition, when liners constructed below the groundwater table
 intersect these pathways, hydraulic pressures can build against the outside
 of the liner.  In unfilled facilities this can result in heaving,  slope
 failure, and  liner rupture.

5.1.1.2  Approach and Methodology—
     The investigation of a facility site should address the following:

       •  Regional  and site-specific investigations to relate the  site
          geology to the  regional geological  picture.

       •  Topography,  including  drainage  patterns.

       •  Analyses  of representative soil  samples.   Important tests can
          include Atterberg limits,  particle  size distribution,  shrink/
          swell potential,  cation exchange capacity,  total  organic
          carbon, mineralogy,  shear strength,  dispersivity,  compres-
          sibility,  consolidation properties,  density  and moisture
          content,  Proctor  density,  laboratory (compacted)  permeability,
          and chemical  compatibility.

       t  In-place  soil characteristics including depth  to  bedrock,
          in-place  permeability, and  the  presence of features  that  can
          act as  failure  planes  or  hydrologic  pathways  (e.g.,  slicken-
          sides,  fractures, faults,  silt  and  sand lenses  and  seams, and
          root holes).

       •   Bedrock characteristics including type,  form,  fractures,  solu-
          tion cavities,  and joints.

       •   Hydrogeologic site characteristics  including depth of the
          water table, horizontal and vertical flow components, hydro-
          geologic pathways, seasonal variability, and location and use
          of aquifers.
                                    5-3

-------
        •   Land  use  and  ownership.

        t   Climate.

 This  information  1s necessary  for  facility design and, to some extent, for
 planning  efficient  borrow  site development.

      5.1.1.2.1  Indirect Methods—Indirect investigative methods include
 collection of existing  site  information and  remote sensing techniques.  These
 methods do not  require  drilling  or excavation and are appropriate for the
 initial stages  of site  investigation.

      Site investigations usually begin with  compilation and review of exist-
 ing information pertinent  to the site.  Sources of information include Soil
 Conservation Service County  Soil Surveys, U.S. Geological Survey topographic
 and surficial geology maps,  published literature, State geological survey
 information, and  county records  of geotechnical tests associated with
 previous  construction projects.  This information can be very useful for
 planning  the scope  and  approach  of further site investigation activities.

      Geophysical  remote sensing  techniques that can be applied during site
 investigation include electrical survey methods, ground-penetrating radar,
 and seismic refraction. All of  these techniques are conducted on the surface
 but provide information about  the  subsurface.  The selection of geophysical
 techniques depends  to a large  degree on the  geologic setting (White and
 Brandwein,  1982).

      Electrical resistivity  surveying can be used to delineate the depth of
 the water table as  well as the presence of subsurface layers or lenses of
 different permeability  that  have .contrasting resistivities (e.g., clay and
 sand  layers).   However, electrical resistivity methods cannot be applied in
 certain geologic  settings where  general subsurface resistivity 1s relatively
 high  and  are best used  in areas  (e.g., the Atlantic Coastal Plain) where
 electrical  resistivities of  subsurface materials contrast strongly (White and
 Brandwein,  1982).   Further information on electrical  surveying may be found
 in the U.S. Environmental Protection Agency  (1978) and Freeze and Cherry
 (1979).
                                                    <»
     Seismic refraction surveys can give valuable information about the depth
 to bedrock, the subsurface bedrock topography, and the condition (fracturing)
 of the bedrock  (Cichowicz et al.,  1981).  In addition, the seismic velocity
 of a geologic material  is altered by the degree of weathering and water
 saturation and  therefore can provide information about the variability of
 these parameters in the subsurface.  However, because of the multitude of
variables that  can affect a material's characteristic seismic velocity,
 seismic results can be difficult to interpret, especially in areas with
complex subsurface geology or  In areas where there is little contrast in
seismic propagation velocities in the subsurface.   For this reason,  limited
exploratory drilling will  usually be necessary in  conjunction with seismic
surveys to confirm interpretations based on this technique (Cichowicz et a!.,
1981).  More detailed information on seismic refraction surveying may be
found in Dobrin (1960).
                                     5-4

-------
      Ground-penetrating radar also has some utility to site investigations
 for locating buried structures and pipes and for indicating depth to shallow
 bedrock.  However, it is limited by a shallow depth of penetration when
 compared to ottrer techniques (White and Brandwein,  1982).

      The advantage of indirect techniques during the early stages of site
 investigation is that their use can reduce drilling costs and costs asso-
 ciated with laboratory tests and analysis.  Much information about a site,
 including an indication of its technical  suitability as a containment facil-
 ity site, can be gained at a relatively low cost.   In addition,  the informa-
 tion gathered indirectly can be used to plan direct site investigations,
 ensuring that these are carried out as efficiently  and economically as
 possible.

      5.1.1.2.2  Direct Methods—Direct methods  of site investigation include
 drilling boreholes and wells and excavating pits and trenches.   The purpose
 of these methods is to expose subsurface  material so that the physical  condi-
 tions  can be observed and  measured (e.g., faults, slickensides,  sand seams,
 depth  to bedrock and to the water table,  penetration tests,  and  in  situ
 permeability)  and to obtain samples of subsurface material  for laboratory
 testing of engineering properties.

     Direct investigations are  conducted  during  the final  stages of site
 investigation  and must provide  sufficient information for input  to  the  facil-
 ity design.  The scope of  investigation necessary to accomplish  this goal
 will vary from site to site according  to  the complexity of the subsurface
 geology, the potential  for seasonal  variability  in  site conditions,  and the
 amount of information about the site that is already available.

     Regulatory personnel  from  the Wisconsin Department of Natural  Resources
 have recently  published the following  recommendations for site investigations
 for clay-lined landfills (Gordon et al.,  1984):

        •  Drill  an adequate number of  soil  borings  across the site  to
           characterize the soil  deposits  within  and beneath  the  site.
           The  borings should extend a  minimum of 25 feet  below the
           anticipated site base grade  or  to the  water table, whichever
           is deeper.
                                                     «
        •  Install  a  sufficient  number  of  water table  observation wells
           and  piezometers  to define  both  the horizontal and  vertical
           groundwater flow directions.

        •  Excavate backhoe  pits  on a grid pattern across  potential clay
           borrow sources to  characterize  their depth, areal extent, and
           uniformity  and to  obtain  samples  of the clay material for
           testing.

        •   Perform appropriate laboratory  tests on samples from the
          potential clay borrow  sources to determine if they will meet
          the design specifications.

These recommendations are presented as examples; detailed exploration needs
are site and facility specific.
                                     5-5

-------
     Subsurface heterogeneities can lead to increased permeability (seepage)
or loss in strength in the foundation.  Where these are suspected, it may be
appropriate to "dig test pits and trenches to identify and determine the
prevalence of these features.  Downhole television monitors also can be used
in boreholes to identify important subsurface features such as faults,
fractures, slickensides, and zones of permeable material.

     Accessible (pits, trenches, and large boreholes) and inaccessible (bore-
holes and wells) methods of site investigation are summarized in Tables 5-1
and 5-2.  These methods are discussed in more detail in U.S. Department of
Interior (1974).  Methods of obtaining disturbed and undisturbed samples
during both accessible and inaccessible site exploration are discussed in
U.S. Department of Interior (1974) and ASTM (vol. 04.08, 1985).  Methods of
conducting laboratory tests of engineering properties on these samples are
discussed in Chapter 3 and Appendix A of this document.  Detailed discussions
of general geotechnical site investigation techniques may be found in
Winterkorn and Fang (1975).

     Hydrogeologic site investigations are necessary for planning the ground-
water monitoring system and for estimating hydraulic stresses that may act on
the facility so that they may be properly considered during facility design.
Further information on conducting hydrogeologic investigations and on
installing monitoring wells and piezometers may be found in U.S. Environ-
mental Protection Agency (1983, 1986a), Fenn et al. (1977), Johnson Division
(1975), and Lutton et al. (1983).

5.1.2  Liner Material Selection and Characterization

     Soil liner materials are selected based on their ability to meet
specific performance standards and the costs to bring the material onsite.
Requirements that must be met for a soil to perform properly as a liner
material include:

       •  Low permeability (usually < 1 x 10~7 cm/s) when compacted

       •  Sufficient strength to support itself and the overlying facility
          components without failure when compacted to the required
          permeability and thickness                 *

       •  Compatibility with waste or waste leachate to be contained (i.e.,
          no significant loss in permeability or strength when exposed to
          waste or waste leachate).

     The U.S. Environmental Protection Agency has compiled data on the
characteristics of soils used for constructing liners in a variety of
locations nationwide (Elsbury et al., 1985; Ely et al., 1983).  These data
are presented in Tables 5-3 and 5-4.  In addition to soil characteristics,
cost considerations also enter into material selection when liner material
must be brought from offsite.

     The In-place, native soil at the facility site is the ideal Uner
material from the standpoint of cost and convenience; this material will be
excavated during foundation preparation and therefore does not need to be
transported to the site.  If the native soil is not suitable as a liner
                                     5-6

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                                                                     TABLE 5-1.  ACCESSIBLE METHODS OF SUBSURFACE EXPLORATION
                   Methods
                                           Procedure
                                  Type of soil and
                                  in-place condition
                                                                                                         Limitations
                                                                                                                                                         Use
             Trenching
             Cuts
             Test pits
in
 i
             Accessible boring
Excavate 3 ft min. width
by hand, dragline, power
shovel, bulldozer prefer-
able; explosives if neces-
sary; min. bracing or
slope unstable soils.
Same as trenching,
performed on gentle to
fairly steep slopes;
steps up slope may be
necessary.

Excavate rectangular hole,
3 ft by 5 ft min. at
working level, by hand or
hand-operated power tools;
explosives if necessary.
Cribbing required over
S ft depth.  Log and
sample as excavation
progresses when sheeting,
Inclined poling, or
notched-box cribbing Is
required in unstable
soils and for ground-
water control.

Drill 28 in.  min. dia.
hole, using heavy power-
operated disc, bucket,
helical augers, single
tube or core barrels in
stable soils; log and
sample as excavation
progresses; casing required
for protection during sam-
pling and inspection.
Coarse-grained soils,
Including those containing
large quantities of gravel
and cobbles, and soft
weathered rock; and all
fine-grained soils, dense
consolidated, wet or satu-
rated or dry and hard;
loose unconsolldated, wet
or saturated and soft or
dry and granular.
                                                                                                   Depth about 20 ft or
                                                                                                   to groundwater or
                                                                                                   unstable material.
Depth to 50 ft,
Infrequently 80  ft,
or groundwater if
pervious strata  and
high flow.
                                                                                                   Depth of 100 ft in
                                                                                                   soil, 150 ft in rock.
                                                                                                   Requires heavy drill
                                                                                                   rig.
                                                            Access  for logging  and  disturbed  sampling for laboratory
                                                            test, for reconnaissance  and  feasibility  design  stage;
                                                            and  for hand-cut  undisturbed  sampling  for final  design
                                                            or for  field  tests  such as  field  density,  permeability,
                                                            full-sized bearing  capacity tests.   Unsatisfactory  in
                                                            unstable cohesionless soils.   Economical  and besjt
                                                            method  for shallow  explorations of  borrow,  foundation,
                                                            and  aggregate deposits.                         '
                                                                                                                              Use same as above, except is more expensive and used in
                                                                                                                              areas of limited access by heavy equipment and for
                                                                                                                              greater depths.  Best method for "hand cut" undisturbed
                                                                                                                              sampling except in unstable soils or below groundwater.
                                                                                                                              Nonaccesslble methods, Table 5-2, recommended for undis-
                                                                                                                              turbed sampling of fine-grained unstable soils bel-pw
                                                                                                                              water table.
                                                            Use same as above for stable soils in place of  test
                                                            pits; very economical if equipment is available and
                                                            area is accessible.
                                                                                                                                                                        (continued)

-------
                                                                                      TABLE 5-1.  (continued)
                   Methods
                                           Procedure
                                  Type of soil and
                                  in-place condition
                                                                                                         Limitations
                                                                                                                                                         Use
             Accessible caissons
             Tunnels and drifts
             Blasting
                                     Same as accessible borings;
                                     casing and air pressure
                                     required in unstable soils.
Excavate accessible holes,
5 by 7 ft min., using hand
or hand-operated power
tools, lagging required.

Expose strata using ex-
plosives and hand or
power tools.
Same as above but primarily
for consolidated dry soils
and bedrock.
                                                              Sane as above, used
                                                              only when caisson 1s
                                                              part of construction.
                                                                                                   Expensive, used only
                                                                                                   under special conditions.
Limited to exposed
faces or outcrops.
                                                            Limited use, used primarily in establishing footing
                                                            grade during construction for Individual caissons,
                                                            under very poor foundation conditions and/or under
                                                                                                                              water.
                                                                                                                                                                                I
                                                            Limited use, for final exploration of dan-site Abutments
                                                            when other methods have disclosed questionable condi-
                                                            tions that cannot be resolved otherwise.
                                                                                                                              Use to expose rock faces and outcrops for rip-rap and
                                                                                                                              crushed aggregate sources and to indicate size and shape
                                                                                                                              of particles that may be expected during quarrying.
             Source:  U.S. Department of Interior, 1974.
ui

00

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                                                                   TABLE 5-2.  NONACCESSIBLE METHODS OF SUBSURFACE EXPLORATION
                   Methods
                                           Procedure
                                   Type of soil  and
                                   in-place condition
                                                                                                         Limitations
                                                                                                                                                         Use
             Auger boring (hand)
             Auger boring (power)
             Drive-tube  boring
O1
 l
            Percussion Jchurn)
            drilling
            Wash boring
 Rotate and force auger
 bit into soil,  withdraw
 and empty when  full.
 Auger bits,  2 to 8 in.,
 helical  or post hole.
 Same  as  above,  using
 powered  drill  rigs.
 auger bits, 4  to  24 in.,
 helical,  disc,  or bucket.
 Over  28  in. considered
 to be accessible.
Force open pipe or tube,
with sharpened edges,
without rotation, into
soil; withdraw and
remove soil.  Thin- or
thick-wall tubing or
pipe, 2 to 8 in. dia.

Chopping and cutting
action by Impact of heavy
chisel-edged bit.  Water
added and cuttings form
slurry that is removed
intermittently by pump or
bailer.  For holes larger
than 4 in.

Chopping and cutting by
Impact and twisting action
of lightweight bit,  and  »
jetting action of circulat-
ing water to remove cut-
tings.  For holes from 2
to over 8 in.  dia.
Fine-grained cohesive, fairly
hard to soft or fine-grained,
noncoheslve, dense to loose,
weakly cemented, or dry or
moist; with particles 1/4 in.
to 1-1/2 in. depending upon
size of auger.

Fine-grained as above, and
coarse-grained soils with
particles as large as 3 In.
depending upon auger.
                                                                  Fine-grained  cohesive  and
                                                                  slightly  cohesive  soils such
                                                                  as  loess,  firm  to  soft clays,
                                                                  and silts.
 Coarse-grained soil
 containing cobbles  and
 boulders,  and hard,  dense,
 fine-grained  soils  and
 rock.
                                                                  Fine- or coarse-grained
                                                                  soils, with small
                                                                  amounts of gravel
                                                                  and few cobbles;
                                                                  fairly hard to soft;
                                                                  weakly cemented to
                                                                  loose; above or below
                                                                  water table.
                                                                                                   About 20 ft,  80 ft with
                                                                                                   tripod;  unsatisfactory
                                                                                                   1n unstable cohesionless
                                                                                                   soils below groundwater;
                                                                                                   slow in  hard soils.
Economical  depth about
40  ft, over 100 ft
with special equipment;
unsatisfactory in
unstable cohesionless
soils below groundwater;
slow In hard, dense  soil.

About 80 ft depending
upon equipment.  Not
satisfactory In coarser
fine-grained soils, clean
sands,  or cohesionless
soils below water table.
Unsatisfactory in
unstable soil or
fractured rock; no
information for log-
ging or samples for
classification.
                                No Information  for
                                logging or samples  for
                                classification; slow
                                in hard or cemented
                                layers.
                            (1)  Advance hole.   (2)  Data for logging.   (3)  Represen-
                            tative disturbed samples for classification,  index
                            tests,  and standard properties tests.   (4)  Access for
                            field penetration  and permeability tests.   (5) Access
                            for  undisturbed sampling.                      '   I
                                                                                                                              Same as above.
                                                            Same as above.
Used with other methods to advance hole through hard,
cemented strata, coarse gravel, boulders, or other
obstructions.
                           (1) Used with other methods to advance hole particularly
                           through unstable soils requiring casing.  (2) Penetrate
                           fine-grained soils to establish depth to bedrock.
                           (3) Drill  holes for groundwater observation.
                           (4) Provide access for sampling and penetration testing
                           of Impervious soils above groundwater or pervious
                           or impervious soils below.
                                                                                                                                                                       (continued)

-------
                                                                                      TABLE 5-2 (continued)
                  Methods
                                          Procedure
                                                          Type of soil  and
                                                          tn-place condition
                                                                                                        Limitations
                                                                                                                                                       Use
            Jetting
            Rotary drilling
            Rotary drilling
Ul

t-»
o
Continuous sampling
                        High-velocity water jet
                        directed downward from
                        pipe raised and lowered
                        In short strokes; erodes
                        soil, which is carried
                        upward by water.  For
                        holes 2 In. to over 10 in.
                        dia.

                        Power rotation of bit;
                        cuttings removed by cir-
                        culation of drilling mud
                        or water; holes 1-1/2 In.
                        to over 10 In. dia.
                        Power rotation of bit;
                        cuttings removed by cir-
                        culation of air.  Holes
                        2 In. to over 10 in. dia.
Drive-tube boring or
rotary drilling (core bor--
1ng) that provides samples
as a result of advancing
the hole.
                             Fine- or coarse-grained
                             soils; weakly cemented
                             noncoheslve or cohesive;
                             above or below water
                             table.
                             Fine- or coarse-grained,
                             compact or cemented soils,
                             and rock.
                             Fine- or coarse-grained,
                             compact or cemented
                             soils and rock.
Ho information for
logging or samples for
classification; slow
in hard cohesive soils.
Ho Information for
logging or samples for
classification;
difficult in loose,
coarse-grained soil with
cobbles and boulders.

Information for logging
and samples for
classification;
unsatisfactory In loose
coarse-grained soil
with cobbles and
boulders.

Depends upon the
method selected.
                                                                                                                             Same  as  (1),  (2),  and  (3)  for wash  boring.
(1) Advance hole.  (2) Access for field penetration test
(not suitable for well permeameter test or groundwater
observation If drilling mud used).  (3) Access for dis-
turbed or undisturbed sampling.
(1) Advance hole.  (2) Access for field penetration
test.  (3) Well permeameter test.  (4) Groundwater
observation.  (5) Access for disturbed and undisturbed
sampling.  (6) Advance hole to install casing for
nuclear moisture-density probes.
            Source:  U.S. Department of Interior, 1974.

-------
                             TABLE  5-3.   PROPERTIES OF SOILS USED TO CONSTRUCT SOIL LINERS*
01
Geographic
Location
Alabama
Al abama
Al abama
California
California
California
California
Colorado
Georgia
1 1 1 i noi s
I ndi ana
Indiana
Michigan
Michigan
New York
Ohio
Oklahoma
South Carolina
Texas
Texas
Utah
Geologic
Origin
residual
residual
sedimentary
sedimentary
residual
sedimentary
sedimentary
residual
residual
glacial
glacial
glacial
glacial
glacial
glacial
glacial
residual
sedimentary
sedimentary
sedimentary
sedimentary
Percent
Passing
No. 200
Sieve
96
75
75
78
95
95
>30
40-80
85
--
57
--
80
80
—
90-98
--
—
--
75-90
Atterberg
Limits
Liquid
L i mi t
62-79
32-48
40-90
35
__
35-60
50-65
--
44-70
19-29
—
23
36
30
30
--
30-45
56
37
—
20-40
Plasticity
Index
29-53
14-28

15
_ _
above A line
above A line
__
20-34
6-15
__
12
20
15
15
—
18-25
35
19
__
5-20
Unified
Classification
CH, MH
CL, CH
CL

CL, CH
CH
. CL, CH

CL, ML

CL
CL
CL
CH

CL,CH
CH
CL

CL, ML
Hydraulic
Conductivity
cm sec-3 '
	 — 1 —
<1.0 x 10-7
<1.0 x 10-7
~6.9 x 10~^
3.5 x 10-6
<1.0 x 10"7
^ J. • W /\ J.V/
<1.0 x 10-7
<1.0 x 10-7
<1.0 x 10-7
6.0 x 10-7
<1.0 x 10-7
<1.0 x 10~7
~8.5 x 10-8
<1.0 x 10-7
<1.0 x 10-8
<1.0 x 10-8
2.4 x 10-8
<1.0 x ID'7
<1.0 x 10-7
2.9 x 10-8
6.0 x ID"9
<1.0 x 10-7
        aData from Part B Permit Applications.

-------
                             TABLE 5-4.   PROPERTIES OF SOILS USED TO CONSTRUCT SOIL LINERS*
01

I—«
ro
Geographic
Location
Unknown
Unknown

Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown
Unknown

Unknown
Unknown
Geologic
Origin

glacial

__ •
• __
_ _
_ _
__
glacial
—
__
__

__
—
Percent
Passing
No. 200
Si eve
31
—

84
78
86
70
80
--
—
__
__

	
—
Atterberg
Limits
Liquid
Limit
28
33-51

31
21-54
40-43
38
29
16-27
25-40
.. . 45
28-39

11-13
42
Plasticity
Index
7
16-32

14
8-30
22-24
20
11
3-10
5-9
18
15-17

3
18
Unified
Classification
CL,ML
—

CL
CL.CH
CL
CL
CL,CH

__
CL
__

__
CL
Hydraulic
Conductivity (
cm sec-1 ,
<1.0 x lO-7
2.9 x 10-8
to 3.5 x 10-8
2.7 x 10-8
<1.0 x 10-8
1.3 x 10-8
<1.0 x 10-7
~2.6 x 10-9
2.0 x 10-8
2.0 x 10-;
1.0 x.10-7..
3.8 x 10-7
to 4.9 x 10-8
1.0 x 10-7
4.9 x 10-8
          aFrom Ely  et al.,  1983.

-------
 material, a suitable soil from a nearby borrow source can be utilized.   Most
 engineers interviewed reported an economic haul  distance of 8 to 10 miles for
 borrow clay, -a-1-though haul distances of up to 25 miles were reported in some
 instances.  When suitable soils are not available at economic distances from
 the facility, it may be necessary to blend an additive, such as  bentonite,
 with the native soil.to improve its performance  as a liner material  or  to
 blend together local soils to achieve the proper material  properties.   These
 solutions are used in areas where suitable clay  is scarce.

 5.1.2.1  Native Soils-
      Native soils include those obtained onsite  and those  obtained  from
 nearby borrow areas.  Design engineers'  opinions differed  over suitable soil
 types for a clay liner.  These differences are,  to some extent,  due  to
 regional  variability in soil  types.  However,  the differences are also  due  to
 the fact that soil  selection based on the desirable characteristics  for liner
 soils (low permeability,  high strength,  self-healing capacity, chemical
 compatibility,  and low settlement and shrink/swell  potential)  involves  some
 compromise between these  characteristics.  The soils with  the lowest
 permeability and the highest flexibility and  self-healing  capacity  (CH  or fat
 clays—see Section 3.4 of this document)  have  the lowest strength and highest
 shrink/swell  potential  and, are more affected  by  chemicals  than other soils.
 Gravelly or sandy clays have high strength and a relatively low  potential for
 settlement.   However,  they also tend to  be brittle and crack when stressed,
 and they may be more likely to contain sandy  or  gravelly inclusions  that
 could locally raise permeability.

      Opinions differ on the suitability  of fat(CH)  clays for liners.  Some
 consider that their tendency to wick moisture; to dry,  shrink, and crack; and
 to  expand upon  moistening,  combined with  a higher likelihood of  permeability
 changes when  exposed to certain chemicals,  makes them inherently unsuitable
 as  liner materials.  Others consider that their  low permeability and high
 self-healing  capacity  makes them the preferred liner material  as long as
 provisions are  made to prevent moisture  change in the liner during construc-
 tion  and  operation  and after closure.   Interestingly,  the  location of the
 persons interviewed seemed  to affect their opinion  on the  use  of fat clays  in
 liners.  Engineers  in  regions where these clays  were common were more
 positive  about  their use  than engineers  in  regions  where these clays are  not
 common  and other clay  types are more readily availably.  However, all
 engineers agreed that  the major factors  influencing  soil selection were its
 cost,  and  its  ability to be  compacted to  the required permeability.

      If sufficient  quantities of soil  suitable for  use as a  liner material
 are not available at the facility site, a borrow source must be  identified.
 When  a  borrow source is selected,  routine  testing procedures are used to
 screen  various potential sites.   The time and expense  involved in permeabil-
 ity testing discourage  its  use  for  this routine  screening.   Design firms
 often estimate clay  suitability  (i.e., permeability  and  strength) based on
 quicker, more easily performed  tests,  including Atterberg limits, gradation
 (particle  size distribution), and compaction tests  (standard Proctor).

     Once a potential borrow  source has been identified, the site should be
 investigated, with the methods described in Section 5.1.1,  to determine  the
amount of suitable soil present at the site and the degree of spatial
variability of soil properties in the soil deposits and to confirm that  the
soil is sufficiently impermeable to serve as a liner material. Borrow source


                                    5-13

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 Investigation  results  then  can be used to plan an efficient extraction
 procedure  for-the  liner material.

      Prior to  facility design, representative samples of the liner material
 are  subjected  to laboratory compaction and permeability tests to establish
 the  relationship among moisture  content, density, compactive effort, and
 permeability.  This  information  is needed for preparation of the facility
 design  and the construction specifications.  Although both standard and
 modified Proctor compaction tests are used, standard Proctor is preferred by
 most engineers because it results in a wetter optimum moisture content for a
 given soil.  Fixed-wall, flexible-wall, and consolidation cell permeameters
 are  used to measure  laboratory permeabilities and to establish the moisture
 content and compactive effort at which minimum permeabilities may be achieved
 (for further discussion of  these techniques, see Chapter 3).

      Strength  of the liner  and foundation soils also must be measured for
 input to the design.  The triaxial compression strength test (ASTM D2850-82)
 is generally preferred for  measuring soil strength.  However, the direct
 shear test (ASTM D3080-72,  D2573-72) or vane shear test may also be used.
 The  shear  test chosen  should mimic the type of failure most likely to occur
 1n the  soil liner.

      The results of  compaction,  permeability, and strength tests are used to
 establish  an envelope  of acceptable values for parameters that will be used
 during  design  to establish  material and compaction specifications.  Suffi-
 cient testing  should be conducted to determine the range of variability in
 these soil  properties  and to determine the suitability of all soil types that
 may  be  encountered at  the soil source.  Correlating these test results with
 soil  Index properties, appearance, and feel enables ranges of acceptable
 values  of  these properties  to be established and specified for routine
 screening  of liner material  as it leaves the borrow source (see
 Section 5.3.4).

      Most  design engineers  interviewed also recommended that compatibility
 studies of liner soils with  wastes or waste leachates be conducted as a part
 of the material selection,  especially when the soils are comprised of fat
 clays.  However, no  cases were uncovered (by the authors) where compatibility
 problems with  a natural soil resulted in rejection ot that soil  as a liner
material.  One of the  biggest problems with compatibility testing is the
 selection  of a representative waste or leachate composition.  Another is
deciding how much of a change in soil properties (e.g., permeability) on
exposure to the waste  or waste leachate constitutes incompatibility.  More
discussion on  the techniques and the problems associated with compatibility
testing may be found in Chapter 4 of this document.

5.1.2.2  Admixed Soils—
     When the  in situ native soil is not suitable as a clay liner and nearby
borrow sources of suitable soils do not exist,  it may be economical  to use
bentonite or other clay materials as a soil  additive to decrease the
permeability of the  native soil.  Bentonite is  a clay material  composed of
mostly sodium-montmorillonite (with minor amounts of calcium-montmorlllonite
and other clay minerals)  and 1s, as a result, highly expansive with the addi-
tion of water.  Bentonite1s  expansive nature enables relatively small  amounts
 (5 to 10 percent) to be added to a noncohesive  soil  and makes it cohesive and
behave similarly to a soil  containing 50 percent nonbentonite clay (Kozlcki


                                    5-14

-------
 and Heenan,  1983).   Blending  two  native  soils  can also be  used to produce a
 soil  with the-desired material  characteristics.

      Important parameters  to  consider  in the design of bentonite liners
 include  aggregate particle size of  the dry bentonite, mineralogy (as
 reflected by swelling potential), and  the required bentonite application
 rate. Both  granular and milled (powdered) bentonite are currently used as
 admixed  liner material.  However, a Canadian firm with extensive experience
 in  designing bentonite liners recommends that  only powdered bentonite be used
 in  liners (Kozicki,  Ground Engineering,  Ltd.,  Regina, Saskatchewan, personal
 communication, 1984)  because  powdered  bentonite mixes uniformly throughout
 the soil  mass, making intimate  contact with the soil grains.  Granular
 bentonite cannot  be  as intimately mixed  with the soil.  A  failure of one
 bentonite/sand admixed liner  has been  attributed to the use of granular
 bentonite (Diamond,  1979).

      The  type of  exchangeable cations  present  in a bentonite influences its
 ability  to lower  the permeability of a native  soil and is  an important
 property  to  control.   Sodium  is the predominant cation in  high-swelling
 bentonite; its high-swelling  capacity  minimizes the amount that must be used
 to  lower  the permeability  of  a  soil.  Other bentonites can contain
 significant  amounts  of exchangeable calcium, resulting in  a clay that has a
 lower swelling capacity.   Thus, it  is  important to select  and specify a
 bentonite that has the degree of swelling desired.  This can be done easily
 with  a simple test (Rollins,  1969).

      The  amount of bentonite  to admix  with the native soil to achieve a
 specified compacted  permeability varies  according to soil  conditions.  In
 general,  3 to 8 percent bentonite will lower the permeability of most
 granular  material to  between  1  x ICT7  cm/s to  1 x ID'9 cm/s (Kozicki and
 Heenan,  1983). However, it is  necessary to determine the  optimum application
 rate  and  moisture content  for the specific soil/bentonite  admixture.  Usually
 this  is accomplished  by conducting  a series of compacted permeability tests
 on  admixtures with different  percentages of bentonite.  Alternatively, one
 design engineer determines the  proper  percentage by the amount necessary to
 bring the liquid  limit of  the soil  to  45 or to produce a CL classified soil
 (Pacey, Emcon Associates,  Inc., San Jose, California, personal communication,
 1984).  Once the  proper percentage  of  bentonite is determined, density,
moisture  content, compactlve  effort, and permeability relationships need to
be  established for facility design  purposes.   Proper soil  percentages for
blended soil  liners can also  be determined through the above procedures.

      All   personnel experienced with  bentonite additives agree that
compatibility tests are especially  critical  for admixed liners.  The high-
swelling  clay minerals are generally more affected by chemicals than other
clay minerals.  As an  example,  sodium-montmorillonlte is  easily changed to
calclum-montmorillonite when  it undergoes ion exchange with solutions high 1n
calcium salts.  This change will seriously reduce the swelling potential  of
bentonite and  thereby  increase the permeability of the admixture.

     One  approach to dealing with  the compatibility problem is to  pretreat
the admixed bentonite with the waste liquid  it  1s to contact.   This  method is
currently being used  for bentonite admixed linings  for brine  ponds.   When
brine is  used to wet  the bentonite admixtures,  all  chemical effects  take
place during   installation,  precluding any change  once the brine pond 1s


                                     5-15

-------
filled  (Kozickl, Ground Engineering, Ltd;, Regina, Saskatchewan, personal
communication", 1984).  Although it may not be reasonable to pretreat benton-
1te with hazardous wastes or waste leachate, it may be possible to pretreat
admixtures with a nonhazardous material that will have a similar effect on
the bentonite.

5.1.3   Facility Design

     Once the site and liner material have been selected and characterized,
the design of the hazardous waste containment facility can begin.  Facility
design  is accomplished through standard geotechnical practices but must be
tailored to the individual site geology and facility operational require-
ments.  The following text summarizes some important points about the design
of clay liners gathered through our interviews and review of the literature.
Other facility components (e.g., leachate collection systems and caps) neces-
sary for proper facility performance are not covered by this document.  More
detailed discussions of earthwork design engineering may be found in refer-
ences such as Winterkorn and Fang (1975), U.S. Department of the Navy (1982),
and U.S. Department of the Interior (1974).

5.1.3.1  Configuration—
     The configuration of the clay liner is determined by the configuration
of the  containment facility, which 1s determined by topography, geology,
hydrogeology, land ownership, existing structures, and waste volume require-
ments.  Generally, facilities are rectangular, but topographic constraints or
land availability can result in Irregular shapes.  Facility size is usually
determined by projected waste volume requirements and planned modes of facil-
ity operation.  However, facility size also can be limited by technical
considerations, such as seismic design criteria.

     Facilities may be excavated below ground, built above ground and
contained by dikes, or built partially above and below ground.  Generally the
designs of clay liners for these types of facilities are similar, except that
dike design is required for aboveground facilities and groundwater control
measures are usually required for facilities sited below the water table
(intergradient design).

5.1.3.2  Foundation Design—                        «
     Foundations for clay liners are designed to control settlement and
seepage and to provide structural support for the liner.  The natural founda-
tion should provide satisfactory contact with the overlying liner, minimize
differential settlements and thereby prevent cracking of the liner, and
provide an additional barrier to leachate migration from the facility.

     5.1.3.2.1  Settlement—Sett!ement is usually not a problem for clay
liner foundations.  Most clay liners are sufficiently thick to withstand some
differential settlement of the foundation soils.  As long as the topography
is fairly uniform and significant soil heterogeneities are not present, dif-
ferential settlement should be minimal.  However, several design engineers
recommend excavating and recompacting the upper 1 to 2 feet of foundation
soil to control local settlement and seepage prior to liner installation.
Several engineers also recommend that foundation settlement analysis based on
the site's soil properties (determined during site investigation) be
conducted during the design of the facility.  These analyses should take into
account the weight of all  facility components on the foundations, especially


                                    5-16

-------
footings for pile-type structures such as leachate collection risers, which,
if  Improperly-designed, can be forced into or through the Uner.  Compensated
foundation, wfttCTi implies that the weight of soil extracted from the site
balances the weight of fill material, also can be used to minimize subgrade
settlement  (Vesilind et al., 1983).  Techniques for conducting settlement
analyses are given in any standard soil mechanics text.

     Haxo (1980) notes that differential settlement is a localized structural
stress phenomenon; therefore, the greater the liner's thickness and elastic-
ity, the greater the tolerance range for differential settlement.  A
sufficiently thick liner can engage in self-healing if the subgrade settles
nonuniformly.

     The ability to predict the extent of settlement depends upon the type of
process anticipated to cause settlement.  Primary consolidation, which is a
reduction in void ratio due to removal of pore fluids by mechanical loading,
generally occurs according to the consolidation theory developed for soil.
Basically,  the theory states that the rate and amount of compression is equal
to  the rate and amount of pore fluids squeezed out of the soil (Anderson,
1982).

     Secondary consolidation (densification) depends upon the applied load
and the chemical and physical nature of the solid particles and the waste.
Therefore,  secondary consolidation is more irregular and less predictable
than primary consolidation and may be significant in settlement of plastic
clay soils, heterogeneous fill materials, organic materials, and other
compressible materials.

     Tertiary consolidation (densification) occurs when the volume of solids
is  reduced.  The effect of tertiary consolidation on mineral soils is
minimal; however, it may be a major concern with organic soils, organic
waste, soluble materials, and materials subject to chemical attack.  Tertiary
consolidation is highly irregular and is influenced by a number of environ-
mental factors that make 1t difficult, if not impossible, to predict
(Anderson,  1982).

     5.1.3.2.2  Seepage—Seepage both into and out of the facility must be
controlled during construction and site operation.  Although the clay and
flexible membrane liners are designed to accomplish this goal, for their
optimum performance and because it may function as a backup liner, the
foundation also should be designed to control  seepage.  For 1ntergrad1ent
facilities, seepage can reactivate slickensides in the foundation soil.  If
these features are present near the toe of sidewall  slopes, slope failures
can result  (Boutwell, Soil  Testing Engineers,  Inc.,  Baton Rouge, Louisiana,
personal  communication, 1984).  Opening of slickensides or joints can occur
from stress removal  by excavation and when soils heave in response to
unbalanced water pressures in underlying permeable strata (Boutwell  and
Donald, 1982).

     Heterogeneities  such as large cracks, sand lenses, or sand seams In the
foundation offer pathways for leachate migration and could cause piping
failures.  Soft spots 1n the foundation can cause differential  settlement,
possibly causing cracks in the liner and damage to the leachate collection
and leak detection system.   Cracks and sand lenses or seams also can cause
                                    5-17

-------
 problems during liner construction if the  facility  penetrates  the water
 table.  An illustration of this problem was  provided  by a design engineer
 during one of"the interviews.   In the case he  cited,  a 2-foot  clay  liner was
 installed without"adequate site investigation  or  foundation preparation.  A
 small  fracture  in the foundation base was  connected to an artesian  (geopres-
 sured) aquifer  30 feet below the landfill  bottom.   The overburden that was
 removed during  construction originally provided confining pressure  on the
 fracture.  After the liner was installed,  hydrostatic pressure in the crack
 exceeded the confining pressure provided by  the liner, causing a rupture of
 the liner.  The expense of excavating the  ruptured  liner and crack, grouting
 the crack, and  pumping the aquifer to reduce the  hydraulic head could have
 been avoided or minimized if adequate site Investigation and foundation
 preparation had been practiced prior to liner  installation.

     Solutions  to these problems include the various  dewatering systems
 (e.g., pumping  wells, slurry walls,  trenching, and  pumping) to lower the
 hydraulic gradient on the facility.(Boutwell et al.,  1980).  Further discus-
 sion on dewatering methods may be found in Cashman  and Haws (1970)„ and
 Section 5.1.3.4.7 describes intergradlent  facility  design in more detail.
 Other  methods to control  foundation  seepage  Include properly keying dikes
 Into the foundation subsoil, selecting impermeable  materials for dike cores,
 grouting cracks and fissures in the  foundation soil with bentonite or other
 grouting material,  and designing compacted clay cutoff seals to be emplaced
 1n  areas of the foundation where lenses or seams of permeable  soil occur.
 Figure 5-1 Illustrates typical  clay  cutoff seal designs.

     5.1.3.2.3   Dike Design—Containment facilities built above ground or
 partially above ground require  dikes  to support the aboveground portion.
 Hazardous waste containment facilities  may be designed to be above ground for
 several  reasons.   Regulations may  require  a  certain distance between the
 facility bottom and  the nearest underlying aquifer or, in some  cases,  the
water  table.  Aboveground  design may  be necessary to achieve this separa-
 tion.   In  regions with high water  tables,  limits placed on excavation  depth
 in  order to prevent  bottom heaving or  rupture may necessitate a partial
aboveground design  (see Section  5.3.4.1.7).  In addition, low-cost,  suitable
dike construction material may  be  readily  available at or near the facility
site, making aboveground construction more economical  than excavated
facilities.
                                                    *
     A  containment facility dike serves as a retaining wall  to resist  the
lateral  forces  Imposed by  the stored wastes.   Design for retaining character-
istics  requires  slope  stability analysis, which is normally accomplished by
using the  Bishop method of slices  (Boutwell et al., 1980).  As the waste
produces much of the  outward force on the dike, the geotechnical properties
of the wastes must be defined.   In addition,  time-related changes in the
properties of both the waste and the dike material resulting from consolida-
tion, settlement, changes  in saturation, or chemical interactions must also
be evaluated  (Boutwell et  al.,  1980).  Figure 5-2  illustrates typical  dike
configurations.

     Erosion resistance and control of desiccation must also be considered
during the design of dikes.  Berms and vegetation  may  be  used to control
erosion.   In arid regions  special designs  incorporating gravel-filled  troughs
1n the dike crest have been used to provide a method to prevent desiccation
                                    5-18

-------
                            • Interior Side Slope
                                        Cut required to overexcavate
                                        permeable seam or zone and
                                        replace with compacted seal.
 Permeable
 Seam or Zone
                                                          Clay compacted in lifts not exceeding
                                                          9" in loose thickness to a minimum of 95%
                                                          of the standard proctor density (ASTMI D-698)
                     - Interior Side Slope
                              Cut required to overexcavate
                              permeable seam or zone and
                              replace with compacted seal.
Permeable
Seam or Zone
                                          Clay compacted in lifts not exceeding
                                          9" in loose thickness to a minimum of 95%
                                          of the standard proctor density (ASTM D-698)
                                                                 Base Grade
Corner
                                        Clay compacted in lifts not exceeding
                                       . 9" in loose thickness to a minimum of 95%
                                        of the standard proctor density (ASTM D-698)
                                                                       Base Grade
         Cut required to overexcavate
         permeable seam or zone and
         replace with compacted seal.
                                          Bottom
                          Permeable
                          Seam or Zone
After Waste Management, Inc.
                             Figure 5-1. Compacted clay cutoff seal.
                                           5-19

-------
                                                     Cover Soil
     Berm
Toe Drain
                                  Homogeneous Dike
                                  and Soil Liner
                                                                 Synthetic Membrane
                                                                 Liners
                                                                     Leachate Collection
                                                                     System
                     HOMOGENEOUS DIKE
 Toe Drain
                                                                  Synthetic Membrane
                                                                  Liners
                                                                     Leachate Collection
                                                                     System

                                                                        Low-Permeability
                                                                        Soil Liner
                          ZONED DIKE
               Figure 5-2.  Dike components and typical configurations.
                                    5-20

-------
 cracking.   If  the  trough  is  kept  filled with water, the exposed upper portion
 of  the  dike can  be kept moist.  For further information on dike design, the
 reader  is  referred to Sherard et  al.  (1963), U.S. Bureau of Reclamation
 (1973), Winterkorn and Fang  (1975), U.S. Department of the Army (1977), and
 U.S. Department  of the Navy  (1982).

     5.1.3.2.4   Sidewall  Design—Sidewall slopes of the hazardous waste
 containment facilities identified during this project ranged from 4 to 1
 (horizontal  to vertical)  to  vertical.  Factors that influenced the selection
 of  sidewall  slopes  included waste volume/landfill area considerations,
 foundation  and liner soil stability, equipment operation constraints, and
 stability of other  facility  components.

     One factor  that influences the choice of sidewall slope is whether the
 sidewall liner is  to be compacted in horizontal lifts or in continuous lifts
 parallel to the  liner surface (Figure 5-3).  Generally, the continuous lift
 method cannot be used for side slopes steeper than around 2.5 to 1 because of
 operational  limitations of compaction equipment.  However, this limitation
 varies according to soil characteristics and equipment type.  In one case,
 described during an interview, continous lifts were compacted on slopes as
 steep as 2  to 1 with a sheepsfoot roller.  However, the facility was small
 the slopes were  short, and the roller had to be both pushed and towed to
 negotiate the slope.  In soils common to Louisiana, a bulldozer can operate
 on slopes as steep as 2 to 1 but tends to tear the liner material.  A slope
 of 2.5 to 1 is recommended for bulldozer operation, and a slope of 2.8 to 1
 is recommended when sheepsfoot rollers are used (Boutwell  and Donald, 1982).

     Some design engineers interviewed preferred horizontally compacted side
 slopes to those with continuous lifts because the former are more stable and
 they allow  steeper slopes and hence greater facility waste capacity.  How-
 ever, most  engineers interviewed believe that, for horizontal  sidewall  lifts,
 the orientation of lift boundaries and the compacted clay fabric perpendic-
 ular to the liner surface increase the likelihood of seepage through the
 liner, limiting the desirability of horizontally compacted sidewall slopes.
Thus, most engineers consider 1t especially critical  to ensure that lifts are
adequately tied together in horizontally compacted side slopes.  However, no
case studies were found during this investigation, which demonstrated
increased seepage due to horizontal  sidewall  lift compaction.

     Other sidewall slope considerations collected during  our  Interviews and
literature review include:

       •  Flexible  membrane liner  (FML)  manufacturers  generally recommend
          that, when an  FML is part  of the  liner system,  sldewalls  should not
          be steeper than  3 to 1.  Tracked  vehicles placing  earth materials
          on FMLs tend  to  stall, spin  their tracks  through the  lodse  earth,
          and damage the  FML  on  steeper  slopes  (Morrison et  al.,  1982).
          However,  FML-lined  facilities  with side  slopes of  1 to  1  were
          encountered during  our survey.  Opinions differed  among design
          engineers on this subject.

      •   For admixed bentonite  liners,  slopes of 3 (H) to 1 (V) are
         generally preferred.  Mechanical spreading methods can be used on
         2.5-to-l  slopes, but this is the marginal case.  Hand placement can
                                   5-21

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                                  Overbuild and
                                  Cut to Slope
                                             • ^
                Horizontal Lifts
               Continuous Lifts
Figure 5-3. Methods of liner sidewall compaction.
                   5-22

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           be used on slopes of 2 to 1, with mixing and compaction performed
           by lowing equipment up and down the slope (Kozicki and Heenan,
                 —
        •  The angle of repose of sand corresponds to approximately a 2-to-l
           slope.  Thus, if a granular leachate collection system is designed
           to extend up the slopes, sidewall  slopes cannot exceed 2 to 1.

        •  Although steep sidewalls with horizontal lifts maximize volume  and
           provide greater stability, construction costs can be greater than
           with continuous lifts because of logistic and scheduling require-
           ments and the extra liner material  that must be used and then
           trimmed away.

        •  With thinner linings (2 to 3 feet),  extra width to accorrcnodate
           equipment may result in the sidewall  lining being thicker than  the
           bottom lining for horizontally compacted sidewalls.

        •  One engineering firm preferred horizontally compacted sidewalls  for
           thick linings (>5 feet)  and continous  sidewall  liner lifts  for  thin
           linings (<2  feet).

        •  One engineer recommended that  4-inch  lifts  (versus 6-1 nch bottom
           lifts)  be used  in horizontally compacted liner  sidewalls.

        t  Slopes  of 3  to  1  or less tend  to collect water  if not properly
           smoothed.

        •  Maximum sidewall  slopes  of 2 to 1 are  advisable for  liners  composed
           of  highly plastic soils  because of the  loss  of  stability of these
           soils when they are saturated  (Day, 1970).   Highly plastic  soils
           contain high  amounts  of  smectite clay minerals.   The  high disper-
           sivity  of these minerals  results in a  loss  of strength upon
           wetting.

     Slope stability analysis must  be conducted  for both  foundation and liner
soils to ensure that shearing stresses developing  within  sidewall slopes
following  excavation or dike  construction will not exceed the available shear
strength of the soil and cause  a failure of the  slope.  The shear strength of
the soil and  its  variability  in the  soil mass, degree  of  saturation of the
soil, pore water  pressure (if effective  stress analyses are to  be performed),
slope height  and  inclination, heterogeneities in  the  soil mass, and expected
stresses on the slope are all important  inputs to  slope stability analyses.
Applicable strength tests for the waste and soil  include a measure of
relative shear strength by  a  cone penetrometer, vane  shear  tests, remolding
index, drained direct shear,  triaxial compression, and consolidation tests.
Strength tests should be selected  to mimic the expected mode of failure in
the soil (Haxo, 1983).

     Several methods of slope stability analysis are currently used.  Classic
limit equilibrium methods are generally used for earthwork design.  These
methods take a free body from the slope and,  using estimates of the forces
acting on  the body, calculate the equilibrium shear resistance of the soil
and compare it to the shear strength of the soil to indicate the factor
                                    5-23

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of safety (Fang, 1975).  Regardless of the specific procedure used for carry-
ing out the computations, the following principles are common to all limit
equilibrium methods:  a potential failure surface is postulated; the shearing
resistance required to equilibrate the assumed failure mechanism (i.e., the
shear stresses required along the failure surface to balance the driving
forces of the unsupported slope) is calculated by means of statics; the
calculated shearing resistance required to maintain equilibrium is compared
to the available shear strength of the soil along the assumed failure plane
(the ratio of the existing strength to induced shear stress is one definition
of a factor of safety); and the mechanism with the lowest factor of safety is
found by iteration.                      ;

     Choosing the method depends to some extent on the properties and
hydrologic conditions of the soils to be evaluated.  For homogeneous soils
with equal pore pressure distributions, methods that consider the whole free
body are appropriate, such as the friction circle method (Taylor, 1948).  If
soil properties vary through the soil mass, the method of slices, which
divides the free body into several vertical slices, is appropriate (Bishop,
1955; Fellenius, 1927).  If straight line failure planes can be identified in
the soil mass, the wedge method can be used (Lambe and Whitman, 1969).  The
wedge method has been recommended for evaluating the stability of clay liners
placed on side slopes (Boutwell and Donald, 1982).  For facilities below the
water table it is necessary to consider pore water pressure, and the effec-
tive stress (total stress minus pore water pressure) should be used instead
of total stress (Fang, 1975).  Methods of stability analysis that consider
these factors Include the Bishop and Morgenstern method (Bishop and
Morgenstern, 1960) and the Spencer method (Spencer, 1967).  Factors that must
be considered when slope stability is calculated in special problem soils are
presented in Table 5-5.

     Essentially two types of slope stability problems occur in clay:
short-term stability (end-of-construction case) and long-term stability
(steady-seepage case).  The short-term case applies just after the excavation
is completed and assumes that time has been insufficient for any water to
move in or out of any representative soil element within the soil profile.
When a soil profile is believed to be relatively homogeneous and without
discontinuities, this is a reasonable assumption and has been used with much
success.  Should the clay have substantial joints and fissures, drainage may
occur so quickly along these discontinuities that the* problem may not be
adequately represented by the assumption (Esu, 1966).  In general, only
short-term stability analysis is necessary for interior containment facility
slopes 1f the facility is to be filled shortly after construction; long-term
slope stability should be considered for the outer slopes of aboveground
facilities (Boutwell and Donald, 1982).

     A factor of safety is customarily calculated during slope stability
analysis.  These factors are based on the values of various parameters that
can affect the stability of a slope.  These include available shear strength
versus required shear strength, required soil cohesion versus available soil
cohesion, actual friction angle versus stable friction angle, actual height
versus stable height, and resisting moments versus moments tending to cause
failure (Fang, 1975).
                                     5-24

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                TABLE  5-5.  FACTORS CONTROLLING STABILITY OF
                     SLOPED CUT,INCOME PROBLEM SOILS
Stiff-fissured Clays
 and Shales
                       Field shear resistance may be less than suggested by
                       laboratory tests.  Slope failures may occur progres-
                       sively and shear strengths reduced to residual  values
                       compatible with relatively large deformations.   Some
                       case histories suggest that the long-term performance
                       is controlled by the residual friction angle which
                       for some shales may be as low as 12°.  The most
                       reliable design procedure would involve the use of
                       local experience and recorded observations.
Loess and Other
 Collapsible Soils
                       Strong potential  for collapse and erosion of rela-
                       tively dry material  upon wetting.  Slopes in loess
                       are frequently more  stable when cut vertical to
                       prevent infiltration.  Benches at intervals can be
                       used to reduce effective slope angles.  Evaluate
                       potential  for collapse as described in DM 7.1,
                       Chapter 1.  (See  DM-7.3, Chapter 3 for further
                       guidance.)

Residual Soils
Sensitive Clays
Talus
Loose Sands
Significant local variations in properties can be
expected depending on the weathering profile from
parent rock.  Guidance based on recorded observation
provides prudent basis for design.

Considerable loss of strength upon remolding generatfjd
by natural or man-made disturbance.  Use analyses
based on unconsolidated undrained tests or field vane
tests.
                       Talus is characterized by loose aggregation of rock
                       that accumulates at the foot of rock cliffs.  Stable
                       slopes are commonly between 1-1/4 to 1-3/4 horizontal!
                       to 1 vertical.  Instability 15. associated with
                       abundance of water, mostly when snow is melting.

                       May settle under blasting vibration, or liquify,
                       settle, and lose strength if saturated.  Also prone to
                       er&sion and piping.
Source:  U.S. Department of the Navy, 1982).
                                    5-25

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     A factor of safety of 1.0 means that the slope is constructed at the
limit of equilibrium; the mobilized stresses equal the available strength.
In practice, "larger safety factors are used for designing slopes for critical
facilities.  The acceptable value of factor of safety depends very much on
whether the slope will be temporary or permanent, whether the analysis is for
short- or long-term conditions, whether conservative assumptions have been
made about soil properties, and other factors.  Temporary slopes are often
designed for factors of safety of 1.2 to 1.5.  Permanent slopes are often
designed with different factors of safety for undrained conditions compared
with drained conditions.  For public earth works projects (e.g., dams) in
California, a safety factor of 2.0 is used.  One design engineer considered
a safety factor of 1.7 to be the minimum acceptable for use on outer slopes
of hazardous waste facilities (Reynolds, California Department of Health
Services, Sacramento, California, personal communication, 1984).

     Static slope stability analysis is appropriate in areas with little or
no seismic risk.  Dynamic slope stability must be considered 1n areas where
significant ground motion can occur (Fang, 1975; also see Section 5.1.3.4.6).

     In summary, the following guidance should be applied to the design and
construction of slopes (Lutton et al., 1979):

       •  Examine, sample, and test to ensure that the foundation is not weak
          and likely to participate 1n displacement.

       •  Conduct detailed engineering stability analyses for any site where
          the consequences of slope failure are serious.  Estimate changes in
          hydrology and seismic stability, identify average and worst case
          patterns, and calculate factors of safety.

       •  When selecting soils, consider soil shear strength, allowing for
          compaction and the corresponding strengthening effect.

       t  Specify slope inclination; decreasing the design inclination
          effectively increases the stability of soil slopes.

       •  Use underdralns, toe drains, cutoffs, and leachate collection and
          disposal systems for seepage control.      *

       •  Allow for freeze/thaw and dry/soak conditions in the selection of a
          sufficiently thick side slope soil.

       •  Compact soil as specified, using field tests for quality control or
          quality assurance.  Prescribe lift thickness.

       •  Consider other miscellaneous factors including toe protection
          (e.g., from flooding conditions) the use of berms or systems of
          berms rather than having a single unbroken inclination, and the use
          of reinforcement to strengthen embankments.
                                    5-26

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      5.1.3.2.5  Bottom Design—The bottom of the containment facility must
 be shaped to facilitate leachate collection,in landfills and drainage in
 surface impoundments and to prevent puddling and ponding on the liner during
 construction.  Most design engineers use a 1- to 2-percent slope for the
 facility base, with 2 percent being preferred.

      Kmet et al. (1981) used an analytical model  of landfill  leakage
 developed by Wong (1977) to evaluate several landfill  design  parameters,
 including clay liner bottom slope.  In general,  increasing the bottom slope
 decreased the liner leakage by providing more rapid movement  of leachate to
 the collection sump.  Leakage rapidly increased  when bottom slopes  decreased
 to below 2 percent.  Bottom slope increase to 5  percent provided additional
 reduction in leakage, with little additional benefit for steeper slopes.

      The configuration of the bottom slope depends  on  the facility  configura-
 tion and the leachate collection system design.   Most  designs incorporate a
 sand/gravel  drainage layer with a system of pipes,  with the liner bottom
 sloping to the pipes and the pipes and underlying liner sloping to  a collec-
 tion sump.  Based on the analytical  model  described previously (Wong,  1977)
 Gordon et al. (1984) recommend a maximum leachate flow distance to  the pipe
 network of 150 feet, and 50 feet has been  stated  as the reasonable  minimum
 due to construction practicalities (Kmet et al.,  1981).  Small  facilities
 may have a pipeless collection system, and one design  engineer interviewed
 preferred a properly designed granular drainage  layer  without pipes to a
 piped system because it precludes the necessity  of  cleaning out pipes.

 5.1.3.3  Liner Design--
      Clay liners are constructed of compacted clay  soils installed  in  a
 series of lifts of specified thickness. The liner  must be sufficiently thick
 and impermeable to retard leachate flow and to provide structural support to
 overlying facility components.  For clay liners,  a  permeability of
 1  x 10-'  cm/s is required by Federal  regulations*.   One design  engineer
 recommended  that a permeability of 1 x lO"8 cm/s  be specified to provide
 a  factor of  safety.

      Liner thicknesses  of 1  to 12 feet of  compacted clay were encountered
 during  the course  of this  study,  although  most design  engineers  recommended
  •£?  i   feet of Clay<   State re9ulations usually  detejmine  liner thickness,
 with  2  feet  (as recommended  by EPA guidance)  as the minimum.  Transit  time
 prediction methods also  have been  used to  specify liner  thickness.

      In general, the liner  is  designed to  be  uniformly thick  over the  entire
 facility except for  thicker  areas  that will be excavated to accommodate  the
 leachate collection  sump and any  leachate  collection pipes  recessed into the
 landfill bottom.  This  is necessary  so that, following excavation for  the
 sumps and  pipes, the  liner will have the uniform, specified thickness over
 the entire landfill  bottom as  illustrated  in Figure 5-4.  In addition to
 this, engineers working for  the Department of Natural Resources, State of
Wisconsin, recommend an extra  foot of  liner under leachate collection lines
 (Gordon et al., 1984).  For further information on leachate collection
systems, see Bass, 1986, and U.S. EPA, 1985, 1986 (pages 39-46), and 1987.
  *A11 permeabilities in this Section are laboratory measurements unless
otherwise specified.
                                    5-27

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01
I
00
Drainage
Layer
Recess for Pipe
                                                                            Leachate Collection Pipe
                                        Figure 5-4. Liner design for collection system pipes and sump.

-------
 Extra liner thickness and compactive effort have been recommended for the
 toes of sidewall slopes to combat seepage and to ensure that the bottom and
 sidewall linersjare adequately tied together.

      Lift thickness is selected by the design engineers and the contractors
 depending upon soil characteristics, the compaction equipment to be used, and
 the required compactive effort.  Lift thickness is usually specified in the
 construction specifications.  The liner lifts must be thin enough so that
 adequate compactive effort reaches the lower portion of the lift.  Emplace-
 ment of thin lifts ensures that the entire lift 1s adequately compacted and
 because more additional compactive effort is transferred to lifts below the
 lift being installed.  However, these advantages must be balanced with the
 added construction expenses associated with thinner lifts since more lifts
 must be compacted to achieve the specified liner thickness.  Interviews with
 design engineers indicate a general preference for loose lift thickness of 6
 to 9 Inches.  However, loose lift thicknesses of up to 15 inches have been
 encountered during our survey, and. a 2-foot lift was used over a sand
 drainage layer at one facility (see Section 5.1.3.3).  Some engineers think
 that adequate compaction can be achieved with thick lifts if heavy enough
 compaction equipment is used.  Four-inch lifts were recommended by one
 engineer for horizontally compacted sidewalls.

      Clay liners may be designed to be installed over the entire facility
 (small  facilities)  or in segments (large facilities and continuous-operation
 facilities).  If the liner is installed In segments,  a beveled or step-cut
 joint between segments (Figure 5-5)  should be specified to ensure that they
 are properly tied together.   A bevel  with an  8 to 1 slope was  specified for a
 large facility where the liner was  installed  in wide  transverse strips
 (Boutwell,  Soil  Testing Engineers,  Baton Rouge,  Louisiana,  personal
 communication,  1984).

      Most admixed bentonite  liners  are  only 4  to 6  inches  thick.   Bentonite
 company  literature  Indicates  that liner thickness can  be  as  small  as 4 to
 6  inches because  of the low permeability (l(r9)  that  can  be  achieved with
 bentonite  (IMC,  1982).   However,  Federal  guidance recommends a  2-foot  clay
 liner, and many States  require  liners up  to 10  feet thick.   Regulatory
 personnel in  some of these States did not  think  that  thin bentonite linings
 satisfy the  regulations.  Besides failing  to meet the  thickness  requirements,
 thin  liners may not provide adequate structural  stability for the overlying
 facility components such as leachate collection  risers and may be hard to
 construct to  uniform thickness.  In general, clay liner thickness and
 permeability  requirements must be independently  satisfied; the use of a clay
 with a lower permeability than required does not justify a thinner liner
 (Boutwell and Donald, 1982).

     Two facilities with bentonite liners are included in the case studies
 section of Chapter 7.  At Site 0, local soils were augmented with 3 percent
 bentomte to achieve the required permeability.  The permeability
 achieved was 8.3  x 10-°; however, a 4-foot liner was still used at the
 site.  In addition, 3 percent lime was added to stabilize the bentonite by
 reducing its swelling capacity (by replacing sodium with calcium in the
 bentomte).  The  same effect and permeability could have been achieved
without lime addition by using lower cost bentonite with a h1gh-calc1um-
montmorillonite content.
                                     5-29

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                Bevel Cut
                Step Cut
Figure 5-5. Methods of keying-in liner segments.
                   5-30

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      Site P presents an approach to achieving  both  low permeability and  high
 strength white minimizing the addition of bentonite.   In  this
 double-clay-Uned. site, the upper liner consists  of a  1-foot compacted
 layer of admixed polymer bentonite and native  soil  (5  x 10~8 cm/s)
 sandwiched between two layers (3 ft above and  1 ft  below)  of recompacted
 native soil of a higher permeability (10-° cm/s).   The lower liner is
 composed of 6 inches of compacted admixed liner underlain  by 5  feet of
 recompacted or in situ native soil.  The sides are  single  lined with 18
 inches of compacted native soil  overlying 6 inches  of  compacted admixed
 soil.  The designers of the site used the recompacted  native soil to provide
 structural strength and protection to the admixed liner with the admixed
 liner providing lower permeability.  It is not certain whether  this liner
 design would satisfy current regulatory requirements,  especially in States
 requiring thick liners.

      Liner system configuration  differs according to the type of containment
 facility.  In landfills,  the clay liner usually lies below a synthetic liner
 that lies below the leachate collection system.   In some cases, the clay
 liner may be sandwiched between  two synthetic  liners or vice versa.  Leak
 detection systems may be  installed between the liners  or under  the liner
 system.   A leak detection system may consist of a sand, gravel, and/or
 geotextile layer underlying the  entire facility (continuous coverage) or
 individual  lysimeters or  other instruments at  specific  points under or
 between  liners  (discrete  coverage).   Collection lines  from the  leak detection
 system either pass  through  the clay liner  or pass under the liner to exit at
 the  landfill  periphery.   The latter design is  preferred by many engineers
 because  objects penetrating a liner offer  potential  pathways for leakage
 through  the liner.

      The  relationship of  the clay  liner  to other system components for a
 waste  pile  is the  same as for a  hazardous waste landfill,  except that a
 primary  synthetic  liner is  not required and thus may not be present in  a
 waste  pile.  The  leachate collection  system will  rest directly on  a clay
 liner  when  it is  the  primary liner.

     The major  difference between the  liner system in an Impoundment  and that
 of a  landfill or waste pile  is that because impoundments by definition  are
 designed for holding  bulk liquids, leachate collection  systems  are  not
 installed on top of the liner.  Surface impoundment  liner  system designs
 incorporating clay liners can consist of a single  clay  liner or may consist
 of a system of  redundant liners  (all clay or clay  and synthetic) with  leak
 detection or collection between or under the liners.  If the wastes are to
 remain in the impoundment after closure, synthetic linings are  required.
 Outlet pipes from leak detection/collection systems  (below the  primary  liner)
may pass through the primary liner or may run under  it  to  the periphery of
 the facility.

     A rip-rap  layer on the upper side slopes of  surface impoundments may be
 necessary to protect against wave erosion (Section 5.1.3.4.2).   A discharge
 structure for loading wastes Into the pond will prevent scouring of the liner
 surface (Section 5.1.3.4.2).  Adequate free board  (sidewalls above  the  liquid
                                    5-31

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surface) to contain runoff from large rain storms should be Included 1n
surface Impoundment designs (U.S. Environmental  Protection Agency,  1982b).

     When clay liners are installed over granular leak detection  layers,  the.
granular layer often does not provide enough stability for compacting the
first lift of liner material.  Techniques that allow equipment to 'bridge'
over sand layers without causing rearrangement and damage include:

       •  The use of a geotextile over the drainage layer (this also prevents
          piping)

       •  The use of lighter compaction equipment that can 'bridge'  the  sand

       •  The specification of thicker lower lifts.

At one large facility, this problem was solved by using a loose lift thick-
ness of 2 feet for the first lift over the sand layer.  The normal  lift
thickness at this site was 15 inches; the use of large compaction equipment
enabled thick lifts to be specified.     ;

5.1.3.4.  Special Design Considerations—
     This section describes some special design practices that are needed to
prevent specific causes of clay liner failure.  A full discussion of each of
these failure mechanisms, along with Illustrative case studies, may be found
1n Chapter 6 of this document.

     5.1.3.4.1  Control of Erosion—Erosion can be a problem during liner
construction and on dikes and freeboard areas in completed facilities.  The
most accurate soil loss prediction tool that is now field-operational is the
U.S. Department of Agriculture's Universal Soil  Loss Equation (USLE)
(W1schme1er and Smith, 1978).  This equation has been used for agricultural
erosion control planning for more than a decade.  The maximum erosion rate
should not exceed 2 tons per acre using the USLE (U.S. Environmental Protec-
tion Agency, 1982b).  Important design considerations for erosion control are
listed below (Lutton et al., 1979):      '

       •  Erosion-resistant soils (erosion resistance is quantified by the
          soil  erodibility factor, K, in the USLE) should be selected.

       •  Dispersive clays and soils in a dispersed condition should be
          protected from erosion or avoided in facility areas where erosion
          can occur.

       •  The overall  landfill  configuration is  important.  The two factors,
          L (slope-length factor)  and S (slope-steepness factor),  in the  USLE
          dominate the erosion aspects of runoff.

       •  It is generally essential  to divert natural  drainage from outside
          the immediate site (through external  runoff diversion)  to prevent
          erosion 1n the facility excavation.

       •  Final  dike slopes  more than 5 feet high should be protected from
          erosion by building  berms  and gutters  along  the top and sides of
          the slope.
                                    5-32

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        •  Vegetation should be started as soon as possible on exterior dike
           waljsjind be well maintained throughout the life of the site.

        •  The use of soil covers is often specified to minimize exposure and
           to protect otherwise bare soil  at the construction site.
           Applications should always be encouraged for intervals when
           construction is interrupted.

        t  A program of long-term maintenance can be used to avoid erosion
           problems after closure of the landfill site.  This is especially
           important for flood-retaining structures for facilities sited in
           the 100-year flood plain.

      5.1.3.4.2  Control  of Scouring—Scouring is the erosion of the  liner or
 sidewalls of a containment facility by the force of moving water. Surface
 impoundments often need to be protected from wave erosion on their upper side
 slopes.  Rip-rap (loose rock) is the most widely used material  for this
 purpose.   Concrete aprons can be used, but studies by the U.S.  Department of
 Interior  have shown that rip-rap is generally more effective and easily
 placed (Small, 1981).   Rip-rap must be properly sized and placed to  result  In
 a stable  protective blanket (U.S. Department of Interior, 1974). One design
 engineer  recommends that a wind rose for  the site and the pond  fetch  should
 be used to determine maximum wave height.  The rip-rap layer can then be
 designed, based  on wave  height and expected fluctuations of liquid levels in
 the pond.  Rip-rap generally is uniform in size, and dumped rip-rap performs
 better than  hand-placed  rip-rap.   More information on the design of  rip-rap
 layers may be found in  U.S.  Department of the Interior (1974) and U.S.
 Environmental  Protection Agency (1982b).

      Clay liners in surface  impoundments  must also be protected from  erosion
 by discharge of  waste  into the impoundment.   At least one clay  liner  failure
 identified during this  study was  attributed  to erosion from discharging
 wastes into  the  pond.  Discharge  structures  used to  reduce  this  erosion
 include concrete or rip-rap  aprons,  discharge tubes  with  upward  facing
 outlets,  and various weirs,  such  as  a  reverse duckbill weir (Day, 1970).

      Johnson and Cole  (1976)  reported  that a  bentonite  liner  in  a papermill
 lagoon was protected from scouring by  covering  with  coarse-grained material.
 First the  liner  was  covered with  3 to  4 inches  of  till, and then a 6-inch
 gravel  cover was placed  over  the  till  in  the most  susceptible areas (e.g., at
 the  base  of  the  aerators).  Sidewalls with 3-to-l  slopes were protected from
 scour by 6 inches  of crushed  stone that was covered with  rip-rap.  No
 problems have  resulted in  this  facility.  Johnson and Geisel  (1979)  reported
 that  a  clay  liner  used in  a municipal wastewater treatment  lagoon was
 protected  by covering with gravel.

      Voigts and  Savage (1974) described a wastewater treatment lagoon lined
with  natural clay.  Rip-rap was added to the slopes to protect against wave
action and erosion, and a concrete scour pad was placed under the aerators to
prevent scouring the liner.  Stone was added around the scour pad out to 35
feet as an additional safety factor to prevent erosion.  The aerator
supports,  which penetrated the clay liner, were sealed with neoprone  water
stops in the middle of  the compacted clay.
                                    5-33

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      5.1.3.4.3  Cold Climate  Design—Failures from operations in cold
 climates  are-minimized  by following  design  considerations outlined by Lutton
 (1979).   Although- these considerations were developed for covers, the follow-
 ing  are  relevant to  liners as well:

       •   Evaluate soil  susceptibility to undesirable frost actions and
           locate the earth barrier below the frost zone.

       t   Maintain an unfrozen  soil  supply.

       •   Consider seasonal scheduling and  alternating the choice of liner
           soils  depending on  the availability of unfrozen materials.

 In addition, temporary  liner  covers  of soil or organic mulch have been used
 for  protection from  freezing  temperatures.

      5.1.3.4.4   Control  of Piping—Piping is a form of internal  soil erosion
 that occurs  below the ground  surface (see1 Section 6.4).  It occurs when fine
 particles migrate away  from a cohesive soil layer and may result from
 physical  causes  (discordant grain size) or  chemical dissolution.

      Compatibility testing  of the liquid waste or leachate and the liner
material  (see Chapter 4)  is a prerequisite  to minimizing piping from chemical
 dissolution.  The compatibility testing can document the chemicals'  effect on
 permeability.  During the  permeability test, observations for signs of
migrating soil particles  should be made and recorded.  Dissolution effects
 (e.g., observation of an  unusual color of effluent) and obvious structural
 changes 1n the soil material  should also be noted.  The waste and liner would
 be considered compatible  and  piping from dissolution would be considered
 unlikely  1f  the  test  showed no permeability increases, no migrating soil
 particles, and no other dissolution effects.

      Four laboratory  tests  to determine soil susceptibility to dispersive
 erosion have been developed by the U.S. Soil Conservation Service (SCS).
 Dispersion tests  are  a  specialized group of tests for characterizing fine-
 grained soils suspected of  having a tendency to erode rapidly.  A major
 conclusion of a  recent  symposium on soil  piping was that these four tests
 should be performed on  soils where piping would cause, unacceptable damage
 (Sherard and Decker,  1977).  The four tests are the pinhole test, a test of
dissolved salts  in the  pore water, the SCS dispersion test, and the, crumb
 test.  The test methods and extensive test data are available in ASTM Special
Technical Publication No.  623.

     When a  clay  Uner  overlies a granular drainage layer, control of piping
 can  be accomplished by  the  incorporation of a filter layer below the clay
 layer.  A filter  layer will have a grain size slightly larger than the clay
and will capture  the migrating clay particles.  For example, clay over gravel
 represents the joining  of discordant grain sizes such that the clay particles
can  penetrate to  the  voids of the gravel.  When a filter is placed under the
clay, Internal erosion  is  largely eliminated.  In addition, the filter would
help to minimize  drainage problems in the sand or gravel  layer (or the
leachate collection system) that occur from clogging by the fine clay
particles.
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      .Filter layers may be composed of geotextiles or a layer of graded
 material.  Resource Conservation and Recovery Act (RCRA) guidance documents
 have been dev«4-0ped by EPA, and these documents contain criteria for select-
 ing filter layers to stop migrating particles and to avoid plugging of
 drainage layers (U.S. Environmental Protection Agency, 1982b).  The criteria
 were developed by the U.S. Army Corps of Engineers and are based on qrain-
 size ratios for the adjacent layers.

      5.1.3.4.5  Control of Desiccation—Desiccation cracks are prevented by
 several testing, design, and construction procedures.  Waste compatibility
 with the liner should be confirmed to avoid cracking from chemical  attack.
 If the waste leachate creates cracks or channels in the liner material,
 alternative liner materials should be evaluated.  The liner material  should
 be tested to determine the liquid, plastic, and shrinkage limits.  These
 criteria may be used to evaluate a soil's cracking potential (Lutton  et  al.,
 19/9).  Tables 5-6 and 5-7 show the expected volume changes associated with
 these indices.  Soils with high volume changes have a greater tendency to
 crack with decreased moisture.

      Clay liners may be subject to developing desiccation cracks during  and
 immediately after installation.  The clay may be protected from desiccation
 after construction by installing a synthetic membrane;  by installing  1 to
 2  feet of soil; or for surface impoundments, by putting liquids into  the
 impoundment immediately after construction.

 A1JUU  5.1.3.4.6  Seismic Design—Earthquakes occur across  the United States.
 Although they  are  less  frequent in  eastern  States, geological  conditions are
 such  that damage from ground  motion is more widespread  in  the  East than  in
 California  when earthquakes do  occur  (see Section  6.8).   If  a  facility
 is  located  in  an area likely  to experience  ground motion  from  seismic  events,
 it  should be designed to withstand  this ground motion.  The  most  likely  types
 of  damage from seismic  events  include  (LARG,  1982):

        • Failure  of  structures  from ground  shaking

        § Failure  of  facility components due  to  soil liquefaction,
          liquefaction-induced  settlement and landslidlng, and soil  slope
          failure  in  foundations and embankments

        •  Failure  of  facility components due to  fault rupture

        •  Landsliding and collapse of surrounding structures.

Of  these  failures, current Federal locational standards protect only against
fault rupture by requiring a 200-foot setback from active faults.  The other
three types of  failure are caused by earthquake-induced ground motion.

     LARG (1982) found that ground motion is much more important as  a failure
mechanism than  fault rupture.  More sites are impacted by ground motion than
by  surface faulting for a given seismic event because the only sites impacted
by  faulting are those actually located on a surface fault trace.  LARG's
study of six hazardous.waste facilities in California also found that
ground-motion-induced failure of tanks and poorly designed surface
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        TABLE 5-6.  RELATIVE VOLUME CHANGE OF A SOIL AS INDICATED BY
                    PLASTICITY INDEX AND OTHER PARAMETERS
Likelihood of volume
change with changes Plasticity index
in moisture Arid regions
Little 0 to 15
Little to moderate 15 to 30
Moderate to severe 30 or more
Humid regions Shrinkage limit
0 to 30 12 or more
30 to 50 10 to 12
50 or more 10 and less
               TABLE 5-7.  SOIL VOLUME CHANGE AS INDICATED BY
                        LIQUID LIMIT AND GRAIN SIZE
Passing No. 200
sieve (%)
>95
60 to 95
<30
Liquid limit
(%)
>60
40 to 60
<30
Probable expansion
(%)
>10
3 to 10
<1
Source:  Lutton et al., 1979.
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 impoundments were potentially the most significant contributors to hazardous
 waste release_during earthquakes.

      The procesTbf designing earthquake-resistant structures may be divided
 into four steps.  They are:

        •  Determining the maximum credible or maximum probable earthquake for
           the site

        •  Determining the expected peak ground acceleration at the site from
           the maximum earthquake, based on regional  and site-specific
           geologic factors

        •  Determining site-specific seismic hazards, such as potential  for
           soil liquefaction, slope failure, and landslides

        •  Designing the facility to withstand peak ground acceleration.

      The current California Water Resources Control  Board hazardous waste
 regulations encompass these steps in addition to requiring a 200-foot setback
 IT ^ly6 Ho1ocene faults.  Specifically, the California Administrative
 code (CAC)  requires the following for new hazardous  waste facilities or
 expansion of existing facilities:

        •  A determination of the expected peak ground acceleration at the
           waste management unit  associated with maximum credible  earthquake
           (CAC Article 9, Section 2595)

        t  Consideration of regional  and  local  seismic conditions  and faulting
           and site-specific surface  and  subsurface conditions  in  the above
           determination (CAC Article 9,  Section 2595)

        •  Use of the  peak ground acceleration  to determine  the  stability  of
          and safety  factors for all  embankments,  cut  slopes, and  associated
          fills  during  the design life of the  unit (CAC Article 9, Section


       • Design  of the waste management  unit  to withstand  the maximum
          credible earthquake without damage to the  structures that  control
          leachate, surface  drainage, erosion, and gas  (CAC Article 4,
          Section 2547).

     Determining  the maximum expected seismic event and the resultant seismic
loading  at the site are the key  elements  in seismic risk analysis.  The two
approaches to this determination are deterministic and probabilistic
(Bernreuter and Chung, 1984).  The first step in both methods is to delineate
regional  (tectonic province) and  local (fault) sources.  For the deter-
ministic method, the next  step is to select the governing earthquake or
maximum  credible earthquake, usually the most damaging historical  earthquake
associated with the site.  Attenuation of the seismic energy with distance
from the source is then determined based on regional  and local subsurface
conditions.  The maximum  (peak) ground acceleration at the site is then
determined based on surface and subsurface site characteristics.
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     The probabilistic approach involves developing an earthquake recurrence
model  for each  source that could impact the site.  The ground motion at the
site from different earthquakes at different distances is calculated (based
on  local and site-specific subsurface geology), and this information is used
to  calculate the probability that a given level of ground motion will not be
exceeded within a specified time period.  One weakness of the probabilistic
approach is that it results in the same probability of occurrence of a large
earthquake for any time period.  In the real world, the longer the time
period since the last earthquake, the mor.e likely it is that another earth-
quake will occur (Bernreuter and Chung, 1984).  In California, the deter-
ministic approach is considered to be the conservative or worst case approach
and is required for determining peak ground acceleration at hazardous waste
facilities and for large public work projects, e.g., dams (Reynolds,
California Department of Health Services, Sacramento, California, personal
communication,  1984).

     In order to adequately estimate peak ground acceleration associated with
the maximum credible or maximum probable earthquake at a site, it is very
important to conduct comprehensive assessments of the regional geology and
adequate site-specific subsurface investigations.  Site-specific subsurface
geology determines the magnitude and direction of propagation of seismic
energy to such an extent that it is impossible to generalize attenuation of
seismic energy with distance for seismic events.  In addition, determining a
site's geology  is necessary for identifying features that are vulnerable to
seismic ground motion such as unstable soil or rock slopes prone to
landslides and unconsolidated, saturated deposits prone to liquefaction-
induced settlement and failure.  Liquefaction is primarily controlled by the
character of ground motion, soil type, soil moisture content, and in situ
soil stress conditions.  Slopes most vulnerable to earthquake shocks are:

       t  Very steep slopes of weak, fractured, and brittle rocks or
          unsaturated loess that are vulnerable to transient shocks due to
          the opening of tension cracks

       t  Loose, saturated sand that may:be liquefied by shocks with sudden
          collapse of structure and flow slides

       •  Sensitive cohesive soils with natural moisture exceeding the liquid
          limit

       t  Dry, cohesion!ess material on a slope at the angle of repose that
          will respond to seismic shock by shallow sloughing and slight
          flattening of the slope (U.S. Department of the Navy, 1983).

     Estimates of ground motion are derived from peak bedrock acceleration at
a site.  The methodology used to determine peak bedrock acceleration should
take into account regional  and local seismicity,  surface and subsurface
geology,  seismotectonic features, faulting mechanisms (e.g., thrust and
strike-slip) and regional  attenuation.  This peak bedrock acceleration is
then modified for site-specific surface and subsurface conditions that focus
or attenuate seismic energy or that are sensitive to ground motion.  These
conditions include type, thickness,  and density of materials overlying the
bedrock,  surface topography,  and depth to groundwater (for liquefaction
assessment).  The goal  of this approach is to define peak ground acceleration
                                    5-38

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 and ground motion response spectra at a site (Reynolds, California Department
 of Health Services, Sacramento, California, personal communication, 1984).
 Peak ground acceleration is then used for tfie seismic design of the
 facility.  Methods for estimating earthquake ground motions may be found in
 Hays (1980).

      Dynamic side-slope stability may be calculated through standard methods
 such as those described by Makdisi and Seed (1978), Sherard (1967), and Seed
 (1975).  Computer programs are also available for designing earthworks to
 withstand seismic events (EERC, 1984).  The risk of densification and
 settlement in response to ground shaking can be reduced by compacting soils
 to densities high enough to prevent further settlement.  The potential for
 liquefaction can be reduced by removing and replacing sensitive (granular)
 soils or by lowering the water table (Eagling,  1983).

      In general, seismic design of earthworks involves building structures
 with more strength,  density,  mass, and thickness.  Deeper foundations,
 greater cross-sectional  area, and better materials are specified for
 seismic-resistant designs.  Size and configuration are also important;
 generally, smaller facilities are more resistant to damage from ground
 shaking.  A safety factor (Section 5.1.2.3.4) also must be incorporated into
 the design (Reynolds,  California Department of  Health Services, Sacramento,
 California, personal  communication, 1984).

      5.1.3.4.7  Intergradient Facility Design—The construction of sites
 below the water table  (intergradient facilities) presents problems due to
 seepage and hydraulic  forces  on the compacted clay liner.  Excavations below
 the water table can  experience hydraulically induced side-slope slippage and
 heave or rupture of  the  foundation base. In addition,  a buildup of water
 pressure behind a recompacted clay liner can threaten the structural  integ-
 rity of the liner.  Although  not allowed in some States (e.g.,  New York)
 intergradient facilities are  constructed in other States (e.g.,  Louisiana)
 where sites with low-permeability soils  above the water table are  rare.

      When the excavation extends below the  groundwater  table, it is  necessary
 to  consider the long-term or  steady-seepage case for slope  stability
 analysis.   For this  case,  pore pressures are assumed to be  in equilibrium arid
 are  determined from  considerations  of  steady seepage (generally  from the
 construction  of a  flow net  or  finite element analysis');  the excess pore
 pressures  generated due  to  the total stress  changes  in  the  slope during the
 excavation  are assumed to  have dissipated.   This  case is analogous to  the
 drained-shear  test, and  effective stress parameters  should be used.  A number
 of analytical  techniques are available that  are appropriate for  intergradient
 design.  Summaries of the available total stress and effective stress methods
 that describe  the particular assumptions on which the methods are based are
 presented  in a  number of foundation engineering texts and technical
 publications  (e.g., Winterkorn and Fang, 1975; Schuster and Krizek, 1978).

     If the clay soil in which the containment facility is excavated is
 located above an underlying permeable stratum (aquifer), there is potential
for heave or rupture of the floor of the excavation.  To prevent this from
occurring, the downward pressure at the interface of the clay soil layer and
the aquifer must exceed the upward hydrostatic pressure.  Where  the width of
the excavation floor is narrow compared to the thickness of the  clay soil
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 layer  over  the aquifer,  the  shear strength of the soil can add substantially
 to  the calculated  stability  of the soil layer.  However, for large floor
 dimensions  with—respect  to clay  layer thickness or for long-term considera-
 tions,  the  overburden weight should exceed the upward hydrostatic force.

     A related but distinctly different problem involves the stability of the
 compacted soil liner.  Assuming  it is properly designed and installed, the
 liner  may be expected to have a  nearly uniform low permeability.  Water pres-
 sure can build up  behind the clay liner sidewalls or under the clay liner on
 the excavation floor, cause  it to separate from the parent soil, and cause it
 to  heave or rupture.  Whether a  liner heaves or ruptures depends on the
 plasticity  of the  soil,  with more plastic soils tending to heave and stiffer
 soils  tending to rupture.  The analysis of this problem involves, again, a
 comparison  between the "uplift" water pressure and total overburden stress
 due to  the  weight  of the liner (soil density and liner thickness) and any
 waste material in  place.

     Control of  these problems may be achieved by at least three methods:
 (1) decrease the depth of excavation into the clay layer, (2) decrease the
 hydrostatic pressure acting  on the bottom of the clay layer, or (3) increase
 the overburden pressure.  Assuming the design depth is an economically based
 decision, the best permanent solution is the added weight of the waste
 material.   However, in the short term the use of some type of dewatering
 system  or soil grouting may  be necessary if the desired depth is too deep and
 results in  excessive uplift  pressures.  If the imbalance of forces is small
 and it  is estimated that the  time period between excavation of the overburden
 and replacement  by the waste material  is short, a method for evaluating the
 rate of heave proposed by Boutwell and Donald (1982)  can be applied.  They
 note that the uplift of  the  bottom of the excavation  must be small  with
 respect to  the effective diameter of the excavation and that the worst case
 occurs when the  underlying permeable stratum is very  thick.  The authors
 indicate that in some cases  the analysis may show additional  dewatering
measures to be unnecessary.

     Dewatering methods  that  can be used to reduce hydraulic head on the
 liner include dewatering wells, slurry wall  cutoffs,  and sump pumping.
 Further Information on the design and applications of these dewatering
 processes may be found in Cashman and Haws (1970).

 5.1.4  Construction Specifications and CQA Plan

     These  documents establish the lines of communication among the contrac-
 tor, design engineer, owner-operator,  and regulatory  personnel  and are
 critical to the  proper construction of a clay liner.   Both specifications and
 the CQA plan must  be proposed prior to the construction.  These documents
 usually must be  approved by  the permitting agency prior to construction and
must be complete and detailed enough to assure them that the liner will be
 properly constructed.
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 5.1.4.1  Construction Specifications—  ,
     The two iypes of construction specifications are:
                                  ?ji.-'        '.~£  ',*

       •  Performance, which specifies a required level of performance for
          the completed facility components (e.g., the liner will have a
          permeability of 1 x 10~8 cm/s).

       •  Method, which specifies methodology and equipment to be used in
          constructing the liner.

 In general, engineers designing clay liners for hazardous waste facilities
 prefer a combination of method and performance specifications.  The
 performance must be specified to ensure that the liner performs as required.
 Most designers consider some method specifications necessary, especially if
 the contractor is not experienced in constructing clay liners for hazardous
 waste facilities and may not be aware of the importance of operational
 methodology in constructing clay liners so that they will not fail.  In
 addition, moisture content, density, and compactive effort must be controlled
 in the field if the specified permeability is to be achieved; specification
 of these parameters helps ensure that it is achieved.  Combination method and
 performance specifications must be very carefully drawn to solve the problem
 of the specified method that does not yield the specified performance.

     Equipment (e.g., sheepsfoot rollers for compaction) and lift thickness
 are usually specified, and maximum clod size and scarification between lifts
 is sometimes specified.  Prior to liner construction most design engineers
 specify the construction of a test fill with the same materials, equipment,
 and methodology that is to be used for the liner construction.  Test fills
 can give the constructor valuable experience with the equipment, methodology,
 and soil to be used during construction and can help convince the constructor
 of the necessity of using certain equipment or methodology.  Test fills are
 also necessary to ensure that the permeability measured in the laboratory can
 be achieved in the field with the equipment to be used in constructing the
 liner.  Test fills are further discussed in Section 5.3.4.1.

     Design tolerances are usually present in the specifications and/or the
QA plan.  Although statistical  methods are available for determining design
tolerances, most engineers use a 'rule of thumb'  method based on their
experience.  A safety factor approach (e.g.,  specifying an order of magnitude
 lower permeability than required)  is one approach.  Another is to allow a
certain percentage of test failures based on  experience during quality
control  (QC) activities.   Specifications usually  include design drawings and
text and for clay liners  often  include the following:

       •  Facility configuration and size

       t  Foundation  preparation

       •  Liner material  characteristics (e.g., index  properties)

       •   Liner thickness  and permeability

       §   Sidewall  slope
                                    5-41

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        •  Bottom slope and configuration

        •  Lif-t-orientation on  sidewalls

        •  Lift thickness

        •  Maximum clod size

        a  Percent Proctor  density

        •  Percent wet  of optimum moisture content

        •  Scarification between lifts

        •  Compaction equipment and number of passes

        •  Test-fill compaction.

 5.1.4.2  CQA  Plan--
     The design  effort does not end with the start of construction but con-
 tinues  until  the facility  is completed.  The CQA plan is prepared prior to
 construction  and establishes the lines of communication and the testing
 program necessary to inform the designers, owner-operator, and regulatory
 agencies about whether the construction process is producing a liner that
 performs as  required by regulation.  The design engineer uses the CQA and CQC
 results to identify unexpected problems encountered during liner construction
 that can necessitate changes in the original design.  The CQA program also
 informs the designers  and/or owner-operator whether the construction
 specifications are being followed by the contractor.  Further discussion of
 CQA and of the CQA plan may be found in Section 5.3 of this document.

 5.1.5   Design Case Studies

     This  section presents, as examples of current practices, important
 design  features  of some of the clay-lined hazardous waste facilities
 identified during the  course of this study.  These examples are presented to
 Illustrate the variability in clay liner design and construction practices.
 Further Information on  these facilities, including diagrams of the facil-
 ities,  may be found in  Chapter 7 of this report.

 5.1.5.1  Site D—
     This  site,  a secure landfill  in the Southeastern United States, has a
 clay liner constructed  of  compacted clay from a nearby borrow area (about
 3 miles  away)  with a maximum compacted permeability of 1 x 10~7.*  The
 Uner 1s 10 feet  thick  and  lies on a low-permeability deposit of opaline
 claystone  or  Fuller's earth.  The facility is constructed below the water
 table, and a  French drain  system was installed around the site prior to
 excavation to  drain the overlying red sand material.   Side slopes are 3 to
 1.  A 17-foot-wide bench with a 3-foot-wide drainage  trench was constructed
at the top of  the opal   claystone.   This bench enabled a  thicker liner to be
 Installed above the claystone unit.  Below the bench,  a  minimum of 10 feet of
  *A11 permeabilities in this section are laboratory measurements  unless
otherwise specified.
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 the claystone was left as a foundation, except for the leachate collection
 sump, which 1-s underlain by 4.5 feet of claystone.  A test fill was specified
 for this facrH-ty- prior to construction to check equipment performance.  The
 clay liner was compacted 1n 6- to 8-inch lifts, with a sheepsfoot roller or a
 smooth drum vibratory roller.  The clay liner is overlain by a flexible mem-
 brane liner (FML).  Each landfill cell is completed prior to Its operation.

 5.1.5.2  Site F—
      This site is a series of five clay-lined landfill cells each lined with
 10 feet of recompacted clay, an FML, and a 1- to 2-foot overlying compacted
 clay layer to protect the FML.  The clay liner was constructed of material
 obtained from a borrow area about 15 miles from the site.  This facility was
 constructed above the ground with dikes to contain the wastes.   The high
 water table at the site, regulatory considerations, and ready availability
 of suitable dike material  (industrial slag)  at the site contributed to the
 selection of an aboveground design.  Foundation preparation included removal
 of industrial  slag and organic silt material  previously disposed on the
 site.

      A test fill  was specified prior to construction.  The liner was con-
 structed in 6-inch lifts with a sheepsfoot roller.  The sidewall  slope is
 2 to 1,  and the sidewalls  were compacted in  horizontal lifts.  The bottom
 slope of the liner ranged from 1 to 2 percent.  The entire liner was
 installed prior to waste placement.

 5.1.5.3   Site  H~
      This facility is a rectangular 9-acre cell  used as a sanitary landfill.
 it is lined with  a 4-foot  clay liner.  Prior  to clay liner Installation,  the
 fill  area was  rough-graded.   Clay was brought to the facility from a nearby
 borrow area.  The variable nature of the borrow area required a soil's tech-
 nician to be present during  all  removal  operations to ensure that the mate-
 rial  met the project specifications.  A technician present at the land-fill
 rechecked the  material  by  performing the required soil  tests as the clay  was
 emplaced.  The liner was compacted in 12-inch lifts with  either a rubber-
 tired  or sheepsfoot  roller.

     This clay liner is  underlain  by two 12-foot x 100-foot  lysimeters  for
 leak detection.

 5.1.5.4   Site  I —
     This facility consists  of three clay-lined  surface impoundments  that
 cover approximately  8 acres  1n a semiarid  region  of the United  States.  The
 impoundments are  lined with  two 5-foot compacted  clay  liners  separated by a
 15-inch granular  leak detection layer.   The Impoundments are  partly above
 ground and partly  below ground and are contained  by dikes.  The dikes are
 12 feet wide on top.

     The  interior  dike sidewall slopes are 3 to 1.  The soil excavated for
 the facility was used as the liner material.   The  liners were compacted in
 8-inch lifts with a sheepsfoot roller.  A 2-foot  layer of sandy soil was
 placed on top of the liner for protection.  Troughs for loading wastes into
 the impoundment were lined with rip-rap.  This facility experienced failure
 from desiccation cracking of the liner because it was left exposed for 7
months prior to waste emplacement.
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 5.1.5.5   Site J—
     This facility  consists of six ponds and a landfill.  The ponds range in
 size from l/2-ttr4  acres.  The bottom liners at this facility consist of two
 recompacted  clay layers separated by a leak detection system.  The lower clay
 Uner  is  1 foot thick and the upper clay liner is a minimum of 5 feet thick.
 The sidewalls are constructed partially underground and partially above
 ground.   The aboveground sections are built upon dikes.  The leak-detection
 system is a  6-inch  drainage blanket that slopes to a trench containing a
 2-inch slotted polyvinyl chloride (PVC) collection pipe (Figure 7-15).  The
 dikes  around the ponds are topped with a gravel-filled trench.  This trench
 1s filled with water to help prevent desiccation of the dikes during dry
 months.

 5.1.5.6   Site K—
     This site in the Western United States consists of six double-lined
 ponds  ranging from  1.2 to 2 acres..  The pond liners were constructed of the
 local  excavated claystone material.  The liner system consists of a 1-foot
 recompacted  basal liner.  Sump and collection trenches are excavated into
 this bottom  liner.  A 1-foot sand layer covers the lower clay liner.  The
 sand layer is overlain with 3 feet of compacted clay.  The liner was
 compacted with a segmented smooth-wheeled roller.  The facility is
 constructed  partially in ground and partially above ground with dikes to
 contain the  wastes.

 5.1.5.7   Site L—
     The  landfill consists of a flat double clay liner on top of which a dike
 was placed to contain the wastes.  The liner extends beyond the dike to form
 the Uner for a 12-foot-wide drainage ditch that encircles the site.

     The  liner system at this facility consists of six layers listed below
 from the  top down:

       •  An 8- to  12-inch drainage layer (sand or gravel)

       •  An 18- to 25-inch compacted clay layer

       •  A  12-inch sand leak-detection layer
                                                     d
       •  A  12-inch compacted clay layer

       •  A  6- to 18-inch compacted soil layer

       t  A  bidim type C34 (synthetic soil  stabilization geotextile) layer.

5.1.5.8   Site M--
     This 12-acre site is designed to consist of three cells of approximately
equal   size.  The facility is lined with 1 foot of recompacted clay.  A
leachate  collection system is above the clay liner, and a leak detection
system lies  2 feet  below the clay liner.  The first cell  was excavated to a
maximum depth of 6  feet.  This provides a minimum of 5 feet of separation
between the  lowest  layer of waste and the highest seasonal  groundwater eleva-
tion.   The sidewalls were excavated to a maximum slope of 3 to 1.   The bottom
slopes 1 percent to the center of the landfill.
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      The clay for the liner was  obtained  from a nearby borrow area.  Prior to
 the placement-of the clay liner,  all  large  rocks,  roots, and other foreign
 matter were r-enwwed from the foundation.  The foundation was then graded to a
 1-percent slope and scarified to  permit better bonding between the foundation
 and the first clay lift.  Uncompacted  liner material was placed in 12-inch
 lifts and moistened as  necessary.  The clay was then compacted with
 "approved" equipment.  Documentation of the specific types of equipment used
 was not available.

 5.1.5.9  Site P«
      The facility consists  of one double-lined hazardous waste cell.  The
 bottom liner  is composed of leachate collection and detection systems as well
 as  a series of  natural  soil  and bentonite/soil liners.  The side liner and
 dike containment system includes a soil and a bentonite/soil liner.

      The bottom liner extends over the entire bottom and 6 feet up the
 sides.   It is a layered system containing two drainage or collection layers
 and two soil  liners.  Proceeding from the top layer downward, the bottom
 liner components are  as follows:

        •  Leachate collection system—1 foot of No. 78 gravel and sand with
           4-inch perforated PVC pipes

        •  Upper soil  barrier—5 feet of compacted soil further subdivided
           into  three  layers:

                3 feet of compacted native soil.  Permeability =
                1 x lO'4 cm/s.

                1 foot of enchanced soil, i.e., native soil  blended with 9- to
                12-percent polymer-treated bentonite.  Permeability on the
                order  of 5 x 10~8 cm/s.

                1 foot of compacted native soil.  Permeability =
                ID'4 cm/s.

        •  Leak  detection  layer—A 1-foot sand/gravel layer with perforated
           pipe  to  detect  leaks and/or to control  seepage through the upper
           barrier.  The  pipes  are connected to several  independent monitoring
           stations to determine the approximate location of any leaking that
          might  occur.

        •   Lower  soil  barrier—A 6-inch layer of enhanced soil,  i.e.,  native
           soil blended with 9  to 12 percent polymer-treated bentonite.
           Permeability on the order of 5 x 10~8 cm/s.

       •  Buffer zone—5 feet of either in situ  or recompacted  native
          soil.  Permeability = 1 x 10~4 cm/s.

     The side liner system extends from a  point 6  feet above  the cell bottom
to the top of the cell.   This section  will  not  have liquid  impounded  against:
it;  therefore, the liner system is not  as  extensive as the  bottom  liner.
                                    5-45

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 Proceeding from the top layer downward,  the  side  liner components are as
 follows:

        t   1 foot of No. 78  gravel

        •   18 inches of  compacted native  soil; permeability =
           1 x lO-4  cm/s

        •   6 inches  of enhanced soil,  i.e., native soil blended with 9-to
           12-percent polymer-treated  bentonite; permeability on the order
           of 5  x 10~8 cm/s.

 5.1.5.10   Site  Q—
     The  landfill consists  of a single containment cell covering an area of
 approximately 3 acres.   It  is located in a former sand and gravel pit.  The
 cell has  a double liner consisting of two 4-inch  layers of a bentonite/soil
 mixture on the  bottom and side slopes up to a vertical elevation of 20 feet
 above the cell  bottom.   The bentonite/soil layers are separated by a 12-inch
 layer of  sand on the bottom of the cell and a 6-inch layer of sand on the
 side slopes.  The side  slopes above the 20-foot vertical level are covered
 with a  single 6-inch layer  of the bentonite/soil mixture.  All bottom and
 side slope bentonite/soil surfaces are covered with a 12-inch protective
 layer of  gravel. The slope of the cell sidewalls varies from 2.5 to 1 to 3
 to  1.

     The  central-plant  (pugmill) mixing method was used "to blend the benton-
 ite.  It  was  spread with a  dump truck, grader, screened boards, and hand
 labor.  A backhoe-mounted hydraulic tamper was used to compact the liner.

 5.2 CLAY LINER CONSTRUCTION:   METHODOLOGY AND EQUIPMENT

     This section describes the methodology and the equipment that are
 presently used  for  constructing clay  liners.  For clarity and convenience,,
 the discussion  is broken down into preinstallation, installation, and
 postinstallation construction phases.

 5.2.1   Preinstallation  Activities

     Before  the liner is installed, the foundation is" prepared, groundwater
 control measures are initiated  for sites below the water table, leak detec-
 tion systems  may be installed, and the groundwater monitoring program is
 implemented.

5.2.1.1   Foundation  Preparation—
     The  foundation  of  a clay-lined hazardous waste containment facility is
the native soil  substrate either unaltered or recompacted.   For aboveground
facilities, dikes constitute part of the foundation.  Operations during the
construction  of  foundations should include the following to accomplish these
goals (U.S. Department of the Army, 1977):

       •  Stripping and  excavating to remove all  soft,  organic,  permeable,
          and otherwise  undesirable materials.  Proof-rolling with  heavy
                                    5-46

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           equipment such as rubber-tired rollers or dozers should be done to
           detect soft areas likely to cause settlement.
        •  Filling of rock joints, clay fractures, depressions,  and any areas
           where undesirable material has been removed.  Fill  material  should
           be engineered backfill compacted to the required specifications or
           grouting material.

 These items are important to ensure secondary containment and to ensure that
 the liner retains its integrity during and after construction.

      Foundation construction will essentially determine the configuration of
 the clay liner.  Whether the foundation is excavated or built above ground,
 the sidewall slope and bottom slope must be properly controlled and shaped.
 Excavation and shaping are accomplished with standard earth-moving equipment
 such as dozers, scraper-pans, and road graders.   Slope control  is achieved
 through traditional  instrument surveying or through electronic  (laser  survey-
 ing) devices.  Trenches are cut for the collection sump and for leachate-
 collection pipes if they are to be recessed into the liner.

      Removal of soft spots and permeable areas in the foundation is
 accomplished with standard excavating equipment.  Once these  are removed, the
 resulting holes and irregularities are backfilled and compacted in a manner
 similar to clay liner construction.  At some facilities,  the  entire founda-
 tion surface is disked or tilled to a depth of 1 to 2 feet and  recompacted in
 one or two lifts.  At other facilites, the foundation is  left unaltered.   At
 the end of foundation construction, the entire landfill base  can be seal-
 rolled (rolled smooth)  to seal  the soil  and to ensure that precipitation  that
 may fall  on the site prior to liner placement will  run off properly and will
 not puddle or pond on the foundation surface. Final  proof rolling also can
 be  used to ensure the integrity of the finished  foundation.

      If the facility is  constructed entirely or  partially  aboveground,  dikes
 are constructed around  the periphery of  the excavation to  serve  as retaining
 walls  for the liner  (see Chapter 7 for examples  of  diked facilities).   Dikes
 are generally earth  or  rockfill  embankments and  are constructed  with the  same
 techniques  and  equipment used to construct  earth  or rockfill  dams.  Founda-
 tions  for dikes  are  prepared  to  control  underseepage,  to provide  satisfactory
 contact with  the overlying  compacted  fill,  and to minimize differential
 settlement  (U.S.  Department of the  Army,  1977).   Dike  foundation  preparation
 operations are generally the  same as  described for  the clay liner  founda-
 tion.  Dikes  may be  constructed  in  horizontal compacted lifts in a manner
 similar to clay  liners.   For  further  information on dike construction,  the
 T^er,,!s  referred to Sherard et al.,  1963; U.S. Department of the Interior,
 1974; Winterkorn and Fang, 1975; U.S. Department of the Army, 1977; and U.S.
 Department of the Navy,  1982.

 5.2.1.2  Groundwater Control--
     When a foundation excavation extends below the water table, unbalanced
 hydrostatic pressures from groundwater can develop  in the foundation bottom
 and sidewalls.  These pressures can cause seepage, sidewall failure and
 collapse, and bottom heave or rupture during subsequent facility construction
and operation.  Groundwater control measures can reduce this hydraulic
                                    5-47

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pressure and thus reduce the likelihood that these failures win  occur.  The
most common methods of reducing hydrostatic head around a facility are:

       •  Construction of a slurry cutoff wall

       •  Trenching and pumping

       •  Installation of dewatering wells for lowering the water table by
          pumping.

     Slurry cutoff walls can be constructed by excavating a trench with a
back hoe (or similar equipment) and backfilling with bentonite, asphalt,
cement grout, or other suitable material.  Alternately, slurry walls can be
installed with the vibrating-beam technique, in which bentonite is injected
along vibrating beams driven into the ground.  Trench and pump methods
involve digging trenches and installing sump pumps to remove infiltration.
Dewatering wells are constructed by standard well-drilling techniques
(Johnson Division, 1975) and are pumped to lower the water table, thereby
reducing hydrostatic pressure on the facility sides and bottom.

     A complete discussion of these techniques 1s beyond the scope of this
document.  For more information, the reader 1s referred to D'Appolonia, 1980;
U.S. Environmental Protection Agency, 1984; Schmednecht and Harmston, 1980;
U.S. Environmental Protection Agency, 1982a; and Cashman and Haws, 1970.

     Groundwater control to preserve liner integrity 1s necessary only during
construction and operation of the facility.  Once the facility is filled, the
weight of the waste will balance the inward hydrostatic forces on the liner,
eliminating the need for groundwater control measures.

5.2.1.3  Leak Detection System Installation—
     If a leak detection system is part of the facility design, it is neces-
sary to install this prior to liner emplacement.  This involves laying
granular drainage layers and pipes over part or all of the foundation.
Following Its installation, the system can be covered with a properly graded
soil blanket or a geotextile to prevent damage during subsequent construction
activities, to provide a stable base for placement of the basal-liner lifts,
and to prevent piping of clay liner material into the porous drainage layer.
For further information on leak detection system desi-gn and installation, the
reader Is referred to related material  on leachate collection systems in
Bass, 1986, and U.S. EPA, 1985, 1986 (pages 39-46), and 1987.

5.2.2  Clay Liner Installation

     Clay liners are constructed by compacting clay soil.  Clay liner
materials covered in this document include natural, untreated soil and soil
mixed with bentonite additives to achieve a lower permeability.  Installation
procedures differ for these materials,  and they will  be addressed separately
in this document.

5.2.2.1  Natural Soil Liners-
     Natural soil liner material may be excavated from the site during
foundation preparation or may be transported to the site from a nearby
borrow source 1f soil material  at the facility is insufficient or if the
1n situ soil is not a suitable liner material.  QC measures are necessary at


                                    5-48

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  the borrow site and/or at the facility to ensure that the liner material
  meets design specifications  (see Section 5.3.4).  Excavation at the borrow
  site is usually-accomplished with 'backhoes," front-end loaders, or other
  standard excavating equipment.  One engineer recommended a side-cut excavator
  for use at the borrow site.  This equipment is apparently very productive and
  produces material with a uniform, small clod size.

      Prior to emplacement, a borrow pile or storage pile of the liner
 material usually is established at the site.  Depending on climatic condi-
  tions and the condition of the clay, the borrow pile may have to be protected
  from moisture loss and erosion.  If the clay is wet when originally placed in
  the pile, protection from moisture loss will reduce the amount of water that
 must be added to the clay prior to compaction.   This is especially important
  in arid climates.  In areas of heavy rainfall,  erosion prevention may be
 necessary to prevent loss of liner material.  Plastic or soil  covers may be
  installed to control borrow pile moisture content and erosion.  Alterna-
 tively,  the pile may be graded and seal -rolled  with motor graders,  bull-
 dozers,  and smooth-wheeled rollers.

      5.2.2.1.1  Liner Material  Emplacement— Thickness requirements  for clav
 liners  for hazardous waste facilities  (usually  2 to 12 feet)  necessitate
 installing the clay in a series  of lifts  (layers)  to ensure  uniform compac-
 tion throughout the liner.  For  each liner  lift, material  from the  borrow
 pile is  emplaced into the facility with  scraper-pans or trucks and  uniformly
 distributed over the site with dozers  or  graders (Figure 5-6).  Lift
 thickness is  controlled during  emplacement  by using measuring  staffs,  shovel
 blades,  or instrument surveys.   Figure 5-7  shows liner material  being
 emplaced in the area of a collection pipe.   The foundation was excavated for
 the pipe,  and, as  a result,  the  lowest liner lift was thicker  in  this  area.
 (This is also illustrated in Figures 5-4  and 7-11.)

   4.^ J:1ner emplacement methods vary with  the size of the facility and  the
 method of facility operation.  For small  facilities,  individual  liner  lifts
 are often  installed over  the entire excavation,  and  the  liner  is  constructed
 as a single unit.   For larger facilities  and for continuous operation  facil-
 ities, where  the wastes are  emplaced in the  facility as  parts  of  the liner
 are built,  the liner is  installed  in segments.   After each liner  segment  is
 .pnmnil6*'  1J  '? .b5v?1!d °f steP-cut with grading equipment so that the next
 segment may be tied  into the previously installed segment, eliminating a
 potential pathway for seepage through the liner along the boundary (see
 Section 5.1.3.3, Figure 5-5).

 .   a5'?'?;J;2. c]od Size Reduction— Following placement, the liner material
 for each 11ft is broken up for homogenization and clod size reduction (clods
 are unbroken aggregates of liner material).  The clod size of the liner
material affects moisture control and compaction operations.  Reduction in
 clod size increases the surface-volume ratio and decreases the time it takes
for moisture to become evenly distributed within the clod (curing time),
thereby facilitating moisture control  operations.  In addition,  clod  size
reduction allows more effective and homogeneous distribution of  compactive
energy through the lift than would be  achieved in lifts  with clods of greater
?QQ! (Nithiam, D'Appolonia  Consulting  Engineers,  personal  communication,
}ffii;    Sey' EMCON Assoc1ates>  San Jose,  California,  personal  communication,
ia«4;.  Homogeneous  compaction  helps ensure  homogeneous  permeability.
                                    5-49

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                           *   ''
Source: Photo courtesy of Wisconsin Department of Natural Resources
                     Figure 5-6. Liner material emplacement.
                                        5-50

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Source: Photo courtesy of Wisconsin Department of Natural Resources
  Figure 5-7. Emplacement of liner material over foundation excavation underneath a
              collection pipe.
                                      5-51

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     Opinions differ among design engineers on optimum clod size for clay
 Uner construction.' Clod size recommendations gathered through interviews
 Include 1 1nch^-2-to 3 inches, no larger than one-half the lift thickness,
 and no larger than  the lift thickness (see Table 5-11, Section 5.3.3.4).
 Clod size reduction is especially important in restricted areas where hand
 compactors must be  used  (e.g., around penetrating objects and in the corners
 of some facilities).  Specifications obtained from the U.S. Department of the
 Navy (1982) and from the nuclear industry require that clod size be reduced
 to 1 to 3 inches in areas that are to be compacted by hand.  Construction
 specifications sometimes specify maximum clod size, but not in most cases.
 In actual practice, clod size may not be carefully controlled.  Clods with
 horizontal dimensions exceeding the lift thickness have been observed by the
 authors at some facilities under construction.

     There is no documented information on the effect of clod size on the
 achievement of specified liner permeability in the field.  However, in a
 laboratory study of compacted clay, Daniel (1981) demonstrated that clod size
 can significantly affect permeability.  Table 5-8 presents the results of
 this experiment.  Daniel  (1984) has also described a field case study where
 large clods and Inadequate curing have resulted in nonuniform moisture
 distribution in compacted clay liners.

     The importance of clod size control depends, to some extent,  on how much
moisture must be removed or added to meet the specified compaction moisture
 content.  If moisture must be added, large clods may necessitate long curing
 times and repeated moisture applications to ensure uniform moisture content
 across the clods, resulting in delays in construction schedules.  Thus,
 efficient clod size reduction can save construction time and money.

     Clod size reduction is usually accomplished using disk harrows or rotary
 tillers with various shaped tilling blades.  Availability usually determines
 equipment selection.  High-speed pulvi-mixers (e.g., BOMAG® MPH 100),
 designed for breaking up soil and old asphalt pavement, have proven to be
 superior to tillers or disks for blending bentonite with soil (Kozickl and
 Heenan, 1983) and may be very good for breaking up soil clumps for untreated
 soil liners (Figure 5-8).  The manufacturer claims that these machines are
 capable of reducing clod size of cohesive soils to 2 inches in a single pass
 and 80 percent of the clods to less than 1.5 inches after two passes.

     5.2.2.1.3  Moisture Control—Moisture control includes the addition or
 removal of water from the liner soil to achieve the specified compaction
moisture content (molding water content).  Correct and uniform moisture
                                    5-52

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  TABLE 5-8.  EFFECT OF CLOD SIZE ON
              PERMEABILITY OF LABORATORY
              COMPACTED CLAY
 Maximum size                  Permeability
of clods (in.)                    (cm/s)
     3/8                         2.5 x 107

     3/16                        1.7 x 1Q8

     1/16                        8.5 x 109


Source:  Daniel, 1981.
                    5-53

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Source:  Photo courtesy of Bomag, Inc.
                 Figure 5-8.  Use of pulvi-mixer for clod size reduction
                                       5-54

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 content is essential for compacting to the specified permeability.   Minimum
 permeability-can be obtained onJy ,,if the molding water content is within
 several percentage points on the "wet side of optimum."  (This is fully
 explained in Chapter 3.)  For this reason, it is important to control  the
 moisture content of the liner material  carefully prior to and during liner
 construction to ensure that the moisture is uniformly applied and distributed
 throughout the soil of each lift.  Nonuniform moisture distribution  in  clay
 liners has been attributed to inadequate breakup of large clods  prior  to
 compaction; uneven water distribution by sprinkling devices,  especially on
 slopes; and inadequate curing time allowed for the  water  to penetrate  the
 soil  (Ghassemi et al., 1983).

      Moisture is added to liner material  prior to placement.   Often  it  is
 most  convenient to do this at the borrow area, although it may be necessary
 to add moisture during liner material  emplacement if the  soil  has dried
 during handling and transport (Figure 5-9).  Moisture addition is accom-
 plished with sprinkler trucks,  sprinkling systems,  or other sprinkling
 devices during spreading and mixing operations.  Added moisture  must be
 thoroughly mixed into the soil  with mixing devices  such as disk  harrows,
 rotary cultivators, or pulvi-mixers, to ensure that moisture  is  uniformly
 distributed throughout the soil  mass.

      Adequate equilibration time after  moisture addition  is critical to
 ensure that moisture is uniformly distributed throughout  the  soil.   Clod size
 reduction  reduces penetration time and  helps  achieve uniform  moisture content
 across all  clods within reasonable time.   Equilibration times may reach days
 or weeks if soil material  is very dry or if soils with a  high montmorillonite
 content are used in the liner.   Moisture addition in the  borrow  area may be
 necessary  in these cases to avoid construction delays that would result if
 the material  were moistened in  place prior to compaction  and  then allowed to
 equilibrate.  In dry areas or during dry periods  of the year,  it may be
 necessary  to cover the soil  during equilibration  to prevent additional
 moisture loss from evaporation.

      If the liner material  becomes too  wet to work  during  construction
 moisture reduction may be  accomplished  through a  combination  of  mechanical
 agitation,  aeration,  and solar drying.

      Moisture content may  be  maintained during  inactive periods  by sloping
 and seal-rolling the  liner to ensure proper runoff  or  by covering the liner
 with  plastic  or  a  layer of moist  soil to  prevent  drying or  overwetting of the
 liner material.   Prevention of drying is  important  because desiccation can
 cause cracking of  the  liner,  which  can greatly  increase its permeability.

      Moisture content measurement  is a QC activity;  techniques for measurinq
 soil  moisture content are discussed  in Chapter 3, and techniques for estimat-
 ing soil moisture during construction are discussed  in Section 5.4.3.2.3.

      5.2.2.1.4  Compaction—The important theoretical aspects  of compaction
of fine-grained soils to achieve low permeability are discussed in Chapters  2
and 3.  Compaction quality control and quality assurance are discussed in
Section 5.3.4.  The discussion below is limited to the practical  aspects of
compaction in the field.
                                    5-55

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Figure 5-9. Moisture addition to liner material prior to compaction.
                            5-56

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      Compaction of a clay liner is accomplished through standard  compaction
 practices as used in other earthwork construction.   The following variables
 exist for compaction operations*   -v        ^  <«

        •  Lift thickness and number

        •  Equipment type and size

        •  Number of equipment passes

        t  Soil  quality         "

        •  Soil  moisture  content.

 Because of their interrelated nature,  it  is necessary to control  all of these
 variables to achieve adequate compaction  in the  field.  Compaction of clay
 soils to obtain low permeability  differs  from  compaction of earth to obtain
 structural  stability in  that compaction is performed at a higher moisture
 content (usually 2 to 3  percent wet of optimum).  Thus, moisture  content is
 one  of the most critical  factors  to control when clay liners are  compacted.

      In a recent study EPA compiled information  on the  compaction practices
 followed during the construction  of a  number of  soil liners (Elsbury, 1985),.
 These data are  presented  in  Table 5-9.  Additional information on construc-
 tion practices  followed  at one German  and 22 U.S. waste disposal  facilities
 was  gathered by Peirce et al., 1986.

      A critical  aspect of the compaction of clay liners is to tie (join)
 together adjacent lifts  properly.   Improperly  tied lifts can result in
 greatly increased horizontal  permeability along  the lift interface, an
 especially serious problem when sidewall lifts are compacted in a horizontal
 manner (see Section  5.1.3.2.4).   Figure 5-10 illustrates joints and seepage
 along lift  boundaries  in  sections  of two experimental liners.  These liners
 were compacted  with  a  small  self-propelled sheepsfoot roller (first figure)
 and  a vibratory plate  hand compactor (second figure).  Two measures recom-
 mended by the interviewed  design  engineers for tying together liner lifts are
 (1)  scarification  of the  surface  of the last installed lift, through a disk
 harrow or other device, before the  next lift is installed and (2)  control  of
 the  moisture content of the adjacent lifts so that they are equivalent and as
 specified.  Haxo  (1983) recommended the use of compaction equipment with feet
 that  are  at  least  50 percent  longer than the height of the compacted lift.
 However, most sheepsfoot  rollers have feet that are 7 to 10 inches long
 (Hilf,  1975), which  could  hamper implementing Haxo's recommendation.

     Johnson and Sallberg  (1960)  reported  on several  studies of the
development of  "compaction planes" or laminations between lifts.   The  results
of these studies indicate the following:

       t  For all types of rollers, laminations or  lift  partings are much
          more likely to  occur in  soils compacted wet  of optimum than  in
          those compacted dry of optimum.

       •  Laminations in  a compacted soil  are produced primarily from
          "springing" of  the lift  under compactive equipment.
                                    5-57

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               TABLE  5-9.   COMPACTION  EQUIPMENT AND  RELATED  SPECIFICATIONS FOR CONSTRUCTING SOIL LINERS
Ul

01
00
Geographic
Location
Alabama

Al abama


Alabama


California


Cal i forma
California

California

Colorado

Compaction
Equipment


— —


Self-propelled
23,000# sheeps-
foot roller
Sheepsfoot roller



Sheepsfoot roller
w/ water ballast
Sheepsfoot roller

20-30 ton sheeps-
foot roller or
Compaction
Moisture
Content
2 to 3% above
optimum
0 to 3% above
optimum

-1 to +3% of
opti mum

+5% of optimum

M

0 to +4% of
opti mum
> +1% of
optimum
+1 to +2% of
opti mum
Maximum*
Density
88-80% standard
Proctor
95% standard
Proctor

95% standard
Proctor

90% modified
Proctor
'1 hi

90% relative
compaction
90% relative
compaction
98% modified
Proctor
Lift Maximum
Thickness Clod Size
! 1
i
15 cm loose

23 cm loose 10 cm nominal
15 cm cmptd effective
di ameter
15 cm loose


15 cm loose —
15 cm cmptd


20 cm loose 2.5 cm
15 cm cmptd
20 cm loose 2.5 cm
15 cm cmptd


                      segmented wheel
                      roller

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                                                TABLE 5-9.  (continued)
01
I
Geographic
Location
Georgia
111 i noi s
Indiana

Indiana

Michigan
Michigan
New York
Ohio
Okl ahoma
South
Carolina
Compaction
Equipment
—
Rubber-tired
roller


—

Vibratory
padfoot
Scraper
traffic
Heavy rubber-
tired roller t
—
Padfoot
Towed vibratory
sheepsfoot
Compaction
Moisture
Content
—
+11 to +13 of
opti mum
__

optimum

—
—

—
2% above
optimum
Wet of optimum
Maximum*
Density
95% max. dry
density
—
90% modified
Proctor
90% modified
Proctor
90% modified
Proctor
93% modified
Proctor
90% modified
Proctor
—
95% standard
Proctor
—
Lift Maximum
Thickness Clod Size
20 cm loose
23 cm loose --
15 cm loose


23 cm loose

--•
20-30 cm
loose
15-23 cm
loose
-- __
15 cm loose 2.5 cm
10 cm cmptd 2.5 cm
15 cm cmptd 2.5 cm

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o>
o
                                               TABLE 5-9.   (continued)
       Geographic
        Location
   Compaction
    Equi pment
  Compaction
   Moisture
   Content
   Maximum*
   Density
  Lift
Thickness
 Maximum
Clod Size
       Texas

       Texas


       Utah
Padfoot
optimum
95% standard
Proctor
                                                            20-23 cm
                                                            loose
                                                                                                            ;  t
               2.5 cm
       ^Specification.

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Source: Photo courtesy of Richard Warner, University of Kentucky
                                    Joints Between Linerlifts
Source: Photo courtesy of Kirk Brown and Assoc., Austin, Texas
                        Joints Between Lifts Coated With Seepage
                 Figure 5-10. Joints and seepage along lift boundaries.
                                        5-61

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        •  Tamping feet tend to mesh  the  boundary between successive layers.

 Because clayilnars must be compacted wet  of  optimum to achieve minimum
 permeability,  this information suggests  that  a great deal of attention must
 be paid to ensure proper bonding  of  clay liner lifts.

      Two methods  of sidewall  compaction  are used for clay-lined hazardous
 waste facilities.  Depending  on soil conditions, if sidewall slopes are less
 than  around 2.5  (H)  to 1 (V),  it  may be  feasible to compact the sidewalls in
 lifts that are continuous with the bottom  liner lifts.  This ensures
 continuity between the liner  bottom  and  sidewalls and also orients the lift
 boundaries and compacted clay  fabric parallel to the liner surface.  However,
 if the sidewall slope  is ,to be steeper than 2.5 to 1, the sidewalls may have
 to be compacted in horizontal  lifts  because most compaction equipment cannot
 operate on such steep  slopes.   When  sidewalls are compacted in a horizontal
 manner, they are  overbuilt  and trimmed back to the final slope with a motor
 grader or excavator.

      Compaction equipment is  usually selected based on techniical performance
 and availability.  Some  of  the technical factors to be considered are whether
 side  slopes or bottom  slopes are  to  be compacted, lift thickness, and liner
 material.  In  some cases technical considerations are not weighed as heavily
 as they should be, and the  choice is made  based on what equipment is
 available that can "do the  job."  The following is a list of the kinds of
 equipment currently used for  compacting  clay  liners:

        •  Sheepsfoot or  clubfoot  roller—self-propelled and towed

        •  Padfoot (pegfoot  or  wedgefoot) roller—self-propelled and towed

        •  Vibratory sheepsfoot roller—self-propelled and towed

        •  Rubber-tired roller

        •  Wobble-wheel,  rubber-tired roller

        •  Smooth-wheeled roller

        •  Vibratory  smooth-wheeled roller

        •  Vibratory plate compactor  (for compaction around penetrating
           objects—hand  operated)

        •  Bulldozers

        •  Tractors.

     Table  5-10 describes the  types and typical  uses of compaction equipment
 (U.S. Department  of the  Navy,  1982).  This table covers all  types of earth-
work compaction operations and  is not limited to clay liner construction;
only that equipment suitable for cohesive soils  at wet-of-optimum moisture
levels  should be  used for clay  liners.   Geotechnical  textbooks  and most
experts  Interviewed recommend the use of sheepsfoot or  tamping  foot rollers
for compacting cohesive  (clay) soils to achieve  low permeability.   The
different types of roller feet are illustrated in  Figure 5-11.   All  of these


                                    5-62

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                                                           TABLE 5-10.   COMPACTION  EQUIPMENT  AND  METHODS
                                                            Requirements for Compaction  of 95  to  100 Percent Standard
                                                                                 Maximum Density
           Equipment
             Type
        Applicability
Compacted
   Lift
Thickness,    Passes or
   in.        Coverages
              Dimensions and Weight of Equipment
                                          Possible Variations in
                                                Equipment      |  '
           Sheepsfoot
           Rollers
For fine-grained soils or
dirty coarse-grained soils
with more than 20 percent
passing No. 200 sieve.  Not
suitable for clean coarse-
grained soils.  Particularly
appropriate for .compaction of
impervious.zone for earth dam
or linings where bonding of
lifts is important.
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           Rubber Tire
           Roller
           Do.
For clean, coarse-grained
  soils with 4 to 8 percent
  passing the No. 200 sieve.
For fine-grained soils or well
  graded, dirty coarse-grained
  soils with more than 8    *
  percent passing the No. 200
  sieve.
           Smooth Wheel  Appropriate for subgrade or
           Rollers         base course compaction of
                           well-graded sand-gravel
                           mixtures.
           Uo	   May be used for fine-grained
                           soils other than in earth
                           dams.  Not suitable for
                           clean well-graded sands or
                           silty uniform sands.
   10
 6 to 8
                                                                     4 to 6  passes
                                                                     for fine-
                                                                     grai ned soi1.

                                                                     6 to 8  passes
                                                                     for coarse-
                                                                     grained, soil.
 3 to 5
coverages
                                                                        4  to 6
                                                                       coverages
                                 8  to  12    4 coverages
                                 6  to  9     6 coverages
                                                                                   Soil Type
                                             Foot       Foot
                                            Contact  Contact
                                             Area    Pressures
                                            sq.  ft.      psi
Fine-grained     5 to 12  250 to 500
soil PI>30
Fine-grained     7 to 14  200 to 400
soil PK30
Coarse-grained   10 to 14 150 to 250
soil            :
Efficient compaction of soils wet of
optimum requires less contact pres-
sure than the same soils at lower
moisture contents.

Tire inflation pressure of 35 to 130
  psi for clean granular material  or
  base course and subgrade compac-
  tion.  Wheel load 18,000 to 25,000
  Ibs.
Tire inflation pressures in excess of
  65 psi, for fine-grained soils of
  high plasticity.  For uniform clean
  sands or silty fine sands, use
  large size tires with pressures  of
  40 to 50 psi.
                          Tandem type rollers for base course
                            or  subgrade compaction 10 to 15 ton
                            weight, 300 to 500 Ibs per lineal
                            in. of width of rear roller.
                          3-wheel roller for compaction of
                            fine-grained soil; weights from 5
                            to  6 tons for materials of low
                            plasticity to 10 tons for materials
                            of  high plasticity.
                                                    For earth  dam,  highway  and
                                                    airfield work,  articulated
                                                    self propelled  rollers  are
                                                    commonly used.   For smaller
                                                    projects,  towed 40  to 60
                                                    inch drums are  used.  Foot
                                                    contact pressure should be
                                                    regulated  so as to  avoid
                                                    shearing the soil on the
                                                    third or fourth pass.
Wide variety of rubber tire,
compaction equipment is
available.  For cohesive
soils, light-wheel loads,
such as provided by wobble-
wheel equipment, may be
substituted for heavy-wheel
load if lift thickness is
decreased.  For granular
soils, large-size tires are
desirable to avoid shear
and rutting.

3-wheel rollers obtainable
in wide range of sizes.
2-wheel tandem rollers are
available in the range of 1
to 20 ton weight.   3-Axle
tandem rollers are gener-
ally used in the range of
10 to 20 tons weight.  Very
heavy rollers are used for
proof rolling of subgrade
or base course.

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                                                                       TABLE S-10.  (continued)
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                                                              Requirements for Compaction of 95 to 100 Percent Standard
                                                                                   Maximum Density
Equipment
Type
Vibrating
Sheetsfoot
Rollers
Vibrating
Smooth Drum
Rollers
Compacted
Lift
Thickness, Passes or Possible Variations in
Applicability in. Coverages Dimensions and Weight of Equipment Equipment
For coarse-grained soils 8 to 12 3 to 5 1 to 20 tons ballasted weight. May have either fixed or
sand-gravel mixtures Dynamic force up to 20 tons. variable cyclic frequency.
For coarse-grained soils 6 to 12 3 to 5
sand-gravel mixtures - rock (soil)
fills ' to - do - - do -
Vibrating     For coarse-grained soils with
Baseplate     less than about 12 percent
Compactors    passing No. 200 sieve.  Best
              suited for materials with 4 to
              8 percent passing No. 200 sieve,
              placed thoroughly wet.
                                                                          4 to 6

                                                            8 to 10    3 coverages
             Single pads or plates should weigh
             no less than 200 Ibs.  May  be used  in
             tandem where working space  is avail-
             able.   For clean coarse-grained  soil,
             vibration frequency should  be no less
             than 1,600 cycles per minute.
                                       Vibrating  pads  or  plates
                                       are available,  hand-
                                       propelled,  single  or  in
                                       gangs, with width  of  cover-
                                       age from 1-1/2  to  15  ft.
                                       Various  types of vibrating-
                                       drum equipment  should be
                                       considered  for  compaction
                                       in large areas.
             Crawler       Best  suited  for coarse-grained
             Tractor       soils with less than 4 to 8
                           percent passing No. 200 sieve,
                           placed thoroughly wet.
                                               60 to 10
 3 to 4
coverages
Vehicle with "Standard" tracks having  Tractor weight up to 85 tons.
contact pressure not less  than 10
psi.
Power Tamper
or Rammer
For difficult access, trench
backfill. Suitable for all
inorganic soils.
4 to 6 in. 2 coverages
for silt
or clay,
6 in. for
coarse-
grained
soi 1 s .
30-1 b minimum weight. Considerable
range is tolerable, depending on
materials and conditions.
Weights up to 250 Ibs.,
foot diameter 4 to 10 in.
            Source:  U.S. Department of the Navy, 1982.

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   Foot
                   (a)
                 Drum
               Tapered or
              Wedge Foot
                                                              Cross Section
                                                              of Tapered Foot
                                                                   (d)
                                                                  Drum
                                                            V3
         Clubfoot
Pegfoot
                                                               Sheepsfoot
Not drawn to scale.

After Johnson and Sallberg, 1960
                Figure 5-11. Sketches of different types of roller feet.
                                    5-65

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 tamping rollers are often referred to  gerierically as  sheepsfoot  rollers.  The
 general consensus is that the kneading action  of these devices affects the
 soil  fabric •hr-a-beneficial  way (see Chapter 3 for a  discussion  of soil
 fabric and permeability).  However, this  opinion is derived from laboratory
 studies of impact versus kneading  compaction,  which show that lower
 permeabilities can be achieved with the latter.  We know of no field studies
 that  demonstrate the superiority of tamping or sheepsfoot  rollers over other
 types of rollers in reducing the permeability  of cohesive  soils.  This is an
 important point because laboratory kneading compactors use a tamping foot of
 about 0.5 inch in diameter,  and the test  procedure ensures that  its impacts
 cover the entire surface area of the test soil.  In contrast, the feet on a
 sheepsfoot roller are several  inches across and are separated on the roller
 by a  space of several  inches (Figure 5-12).  Thus, they do not induce shear
 strains as intensely or as uniformly through the soil mass as the laboratory
 technique does.

      One engineer interviewed related  a case in which the  required compacted
 density for a clay liner could not be  achieved with a sheepsfoot roller but
 was achieved with a vibratory smooth-wheeled roller.  The  differences between
 permeabilities for the two types of rollers were not  determined  in this
 case.  An interview with another design engineer revealed  that at another
 site  (South Central  United States) adequate compaction in  near-saturated
 clays was being achieved with several  passes of a bulldozer.  One major engi-
 neering firm interviewed requires  by specification that for cohesive soil
 compaction at nuclear power  plants a variety of equipment  (including a towed
 sheepsfoot roller,  a self-propelled static wedgefoot  roller, and a towed
 static wedgefoot roller)  be  evaluated  with several different lift thicknesses
 in  a  test fill  prior to construction.   This facilitates selection of the most
 suitable equipment  and lift  thickness  for each soil type to be compacted (see
 section 5.3.3.1).

      Hilf (1975) mentions that sheepsfoot or clubfoot rollers are preferable
 to  other roller types  because  their mixing action produces a more homogeneous
 liner with  respect  to  moisture content  and physical characteristics.  Hilf
 (1975)  also  states  that pad-type tamping  foot  rollers, because of larger foot
 end areas, do  not blend and mix  embankment materials as effectively as
 conventional  sheepsfoot rollers.  Figures 5-11 and 5-12 illustrate the
 difference between  sheepsfoot  and padfoot (or pegfoot.) rollers.

     The  size and configuration of a facility may place some limits  on
 equipment selection.   Large compaction  equipment (necessary for  thick 11ft
 compaction) may not be  usable  at small   sites because of large turning
 rad11.   If sidewalls are  steep, some equipment may not be able to negotiate
 the slope.  Sidewall slopes of 2.8 to 1 or less have been recommended for
 sheepsfoot rollers  (Boutwell and Donald, 1982).  Figure 5-13 shows the
 compaction of a 2-to-l  slope with a sheepsfoot roller.  In this  case it was
 necessary to both push  and tow the roller to negotiate the slope.  If
 sidewalls are compacted  in horizontal  lifts, lift width may restrict the size
 of the  compaction equipment.

     The number of passes necessary to achieve the specified compactive
 effort depends upon the size, weight,  and configuration of the equipment.   In
general, small equipment  requires more passes  than  large equipment.
Compactive effort can be  estimated from the towing  force required to tow the
equipment per unit distance multiplied by the  number of equipment passes.   It


                                    5-66

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Source: Photo courtesy of Wisconsin Department of Natural Resources
   Figure 5-13.  Compaction on a 2(H) to 1(V) slope with a towed sheepsfoot roller.
                                     5-69

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 1s usually expressed on a per unit volume of fill  basis  (e.g.,  foot  pounds
 per cubic foot) (Selig, 1982; Johnson and Sallberg,  1960)  as  follows:
      ( J ( ) (L) „ compactive effort per unit volume  of  fill  (ft  lb/ft3),
      (W) (T) (L)                                                       }'
 where:

      F  *  draw bar pull  (Ib)

      N  *  number of passes

      L  3  length of each pass (ft)

      W  =  roller width  (ft)

      T  =  lift thickness (ft).

      For each  soil/moisture content/equipment combination, a different  num-
 bers  of passes  are required to achieve  a specified permeability and density.
 Thus,  it 1s extremely important  to determine  the compactiye effort necessary
 to  achieve the  design permeability with each  type of  compaction equipment to
 be  used 1n a test fill prior to  construction  (Section 5.3.3.1.1).  Mitchell
 et  al.  (1965) demonstrated that, with some  clays, Increasing compactive
 effort can decrease permeability hundredfold  without  changing density or
 moisture content by additional shearing that  breaks down soil structure.
 Compaction should be controlled  in the  field  by measuring density, moisture,
 and compactive  effort.  The specified values  are based on the relationship,
 previously derived 1n the laboratory and confirmed 1n the field test fill,
 among  these variables and the permeability  for the specific soil and the
 specific compaction equipment to be  used.

     Moisture content, density,  and  compactive effort measurements are  neces-
 sary  for controlling compaction  to ensure that the specified permeability is
 achieved 1n the field.  Visual observations of construction operations  are
 also critical to compaction quality  control.   A full discussion of compaction
 quality control  1s  found  1n Section  5.3.

 5.2.2.2  Admixed Bentonlte Liners—                  *
     In areas where suitable  soils for  clay liners are not available or
 cannot  be economically delivered to  the construction site, bentonite addi-
 tives may be blended Into the unsuitable native soils to enable them to be
 compacted to the required .permeability.  Selection of the type and the proper
 percentage  of bentonite additive 1s  described  1n Section 5.1.2.  The differ-
 ence between Installation of  natural soil liners and bentonite admixtures
mainly  lies  in  the  liner  emplacement methods.  When bentonite 1s stored
 onslte,  1t  is critical to keep 1t covered and  protected from precipitation as
 1t cannot be worked  1n the  wet state.

     5.2.2.2.1   Bentonite Mixing and Spreading—When bentonite soil  additives
are used, they must  be thoroughly and uniformly mixed with the native soil.
                                    5-70

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 This 1s most easily done when the native son is relatively dry.   Mixing  can
 be accomplished in place with the additive applied evenly over the site and
 then mixed iirtp the native soil, or mixing can be done in a central  plant
 where the add!Lives and soil are blended lira mixing device and the  final
 mixture is spread over the site.

      Central plant mixing is the preferred method of several  design  engineers
 interviewed and in a study by Lundgren (1981) has been shown  to be more
 effective than tilling in place.  In this method, the bentonite and  the soil
 are mixed in a pugmill, cement mixer, or other device where moisture is added
 during the mixing process.  Moisture content, particle size,  and  bentonite
 content must be monitored and controlled during this mixing process.  Central
 plant mixing is illustrated in Figure 5-14.   Laboratory tests of  central
 P^nt mixing of bentonite and soil  yielded the following results  (Lundgren,


        •  More than  10 minutes mixing time 1s preferable.

        •  The soil may be dry, naturally conditioned (drained), or saturated
           when the bentonite is added.

        •  Water  should be Introduced into  the mixer  after the  bentonite and
           after  a couple  of minutes  of homogenizing.

        t  All  investigated  bentonites  (five types) were  homogenized to the
           same degree.

 Following  central plant mixing,  spreading may be  accomplished as with natural
 soil  liners  (using trucks or pans and graders or  dozers) or with a continuous
 asphalt  paving machine  (Geo-Con, 1984).

      Currently,  central plant mixers are commercially available that are
 specifically  designed  for bentonlte/soil admixtures.  These mixers are
 capable  of producing 1,000 yd3/day of admixed material.  Computer
 controls for  these devices are capable of achieving an accuracy of +0.5
 percent moisture 1n the admixture throughout  the  project (Geo-Con, T984).

      In-place  spreading and mixing Is a commonly  practiced construction
 method for bentonite/soll liners.  Locally available^lner material 1s first-
 spread uniformly over  the prepared foundation.  The bentonite 1s then spread
 uniformly  over the native Uner material.  If the side slopes are  steep
 (  Lto  Lor 9reater) or the  Uner is small,  bags of bentonite can be placed
 on the site in a predetermined pattern and then the bentonite 1s manually
 raked over the Uner material.  Bag placement must be determined carefully so
 that  the specified quantity of bentonite per  cubic foot of Uner 1s
maintained uniformly throughout the fill.  This is frequently accomplished by
 placing the bags of bentonite  1n a grid pattern over the facility  site.
Close visual scrutiny is necessary during manual mixing to ensure  that the
 spreading  1s adequate.  Alternatively, for larger sites with sldewall slopes
of 2.5 to  1 or less,  mechanical or pneumatic spreaders can be used.  A belt-
feed cement spreader has been found to be particularly suitable for benton-
ite.  This spreader,  pictured 1n Figure 5-15,  requires only two men and
provides uniform spreading rates at up to 25 ton/hr (Koz1ck1 and Heenan,
1983).  The spreader  can be operated with feed from dump trucks or, when
                                    5-71

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                       Source: Photo courtesy of Geo-Con, Inc., Pittsburgh, Pennsylvania
                                               Figure 5-14.  Central plant mixing of bentonite and soil.

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Source: Photo courtesy of Ground Engineering, Ltd.. Regina, Saskatchewan
                        Figure 5-15.  Truck-loaded bentonite spreader.

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ut
i
                           Source: Photo courtesy of Ground Engineering, Ltd.. Regina, Saskatchewan
                                               Figure 5-15. Truck-loaded bentonite spreader (continued).

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  modified with  a  cyclone,  fed  pneumatically  in bulk from tank trucks
  (Figure 5-16)-
              ________             ..$* . >••"•         :>'** r>t
       Following in-place spreading, the bentonite must be mixed into the soil
  along with enough water to bring the mixture to the proper moisture content.
  This  step activates  (swell) and disperses the bentonite.  Mixing can be
  accomplished with disk harrows, rototillers, tined rotovators, or a high-
  speed pulvi-mixer (soil stabilizer).  Disks (Figure 5-17) and tillers should
  make  several passes  in a  crisscross pattern to help break up clods and ensure
  more  complete mixing  (Ghassemi et al., 1983).  Water may be added from
  sprinklers attached  to the mixer or by sprinkling between passes.
  Rototillers have been demonstrated to be more efficient at mixing than disk
  harrows (Ghassemi et al., 1983), and larger wheeled rototillers are more
  effective than the wheel! ess  types (Lundgren, 1981).  Six or eight passes are
  generally required for adequate mixing.                            Ha««

  4. u-^ Severa1 Canadian  installations, a high-speed pulvi-mixer (soil
  stabilizer) achieved very good mixing to a depth of 200 mm in the first pass
  ana to a depth of 300 to 350 mm on subsequent passes (Figure 5-18).  Water
  can be added after the first dry-mix pass (ICozicki and Heenan, 1983) or, as
  illustrated (Figure 5-18), it can be added during mixing.  Two passes are
  generally sufficient to mix the bentonite thoroughly and reduce all clods to
  less  than 1 inch.  Although this equipment is considerably more expensive
  than  conventionally used mixing devices, the reduced number of passes and
  ensurance of better mixing make it cost competitive (Kozicki, 1983, Ground
  Engineering Ltd., Regina, Saskatchewan, Canada,  personal  communication).

  4   ,In7?lac? sPread1"9 and mixing are generally recommended only for
 single-lift (4- to 6-inch) liners; for thicker liners,  the central  plant
 method is  preferred.  One contractor with admixed liner Installation
 experience has stated that because of the difficulty of conducting  stringent;
 quality assurance/quality control  for in-place spreading  mixing,  Eentral
      e"111/?   9  1f««_?  Preferred metnod f°r hazardous waste  containment facility
        (Kyan, 1984).
      5.2.2.2.2  Compaction— Foil owing spreading arid mixing,  the bentonite
 admixture is  compacted.   Vibratory smooth-wheeled rollers  or vibratory-plate
 compactors are preferred for this  operation,  for two reasons.   First,  because
 admixed  liners are  often thin (4 to 6 Inches),  tamplng-foot  or  sheepsfoot
 rollers  can penetrate  the Uner.   However,  this may not  be an Issue  for
 hazardous waste facility liners because most  regulations require  liners
 L ?e:-  h1ck  or sreater.  The second reason stated  for this  preference 1s
 that  the native soils  used, at these sites often have a high  sand  content and
 are most effectively compacted with smooth vibratory rollers  (Kozlckf, Ground
 Engineering,  Ltd.,  Regina, Saskatchewan, Canada,  personal  communication,
 i y GV j •

 5.2»2.3   Climatic Effects—
     The  following  section 1s  a discussion of climatic Influences on clay
 liner construction  activities  and  the measures  to avoid  problems  resulting
 from climatic  stresses.

 ...  5'2.2.3.1  Precipitation  and Desiccation— Precipitation can  Interfere
with construction operations by eroding or flooding the  site or by
                                     5-75

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Ol
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                          Source: Photo courtesy of Ground Engineering, Ltd.. Regina, Saskatchewan
                                                Figure 5-16.  Pneumatically fed bentonite spreader.

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Ul
I
                         Source: Photo courtesy of Ground Engineering, Ltd., Regina, Saskatchewan
                                           Figure 5-16. Pneumatically fed bentonite spreader(continued).

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Figure 5-17. Blending bentonite with soil using a disk harrow.
                         5-78

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U1

 I  ,
VJ

(O
                             Source: Photo courtesy of Ground Engineering. Ltd., Regina, Saskatchewan
                                                   Figure 5-18.  Soil stabilizer mixing bentonite in place.

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 over-moistening  the  Uner material.  Provisions for protecting a borrow pile
 from erosion  or  overwetting have already been discussed.  For Uner Installa-
 tion,  when  construction  1s interrupted at night or by rain, the compacted
 11ft 1s  usua44y-s~eal -rol 1 ed (rolled smooth with a smooth drum or wheeled
 roller).   If  the site  is properly graded, this ensures that water will  run to
 the  lowest  point of  the  site and not puddle or pond on the Uner surface.

      Two  hazardous waste management companies have used or suggested
 Inflatable  domes over  secure landfills for protection from the elements dur-
 ing  construction and operation  (Figure 5-19).  These domes enable construc-
 tion activities  to proceed despite inclement weather.  In addition, for
 facilities  with  continuous operation where wastes are emplaced in the
 landfill  while other parts of the liner are still being constructed, the dome
 prevents  rainwater from  falling on the site, thus eliminating the need to
 collect and treat leachate generated during operation.  Upon closure of the
 facility, the dome is  deflated and moved to another location.

      Plastic  covers may  be used during inactive periods to prevent drying or
 wetting of  the Uner material.  Soil covers are sometimes used to prevent
 desiccation and  erosion.  It 1s important to protect the liner against desic-
 cation, especially if  high-swelling soils have been used, because desiccation
 cracks can  seriously Increase the liner's permeability.  In certain areas, 6-
 to 8-inch dessication  cracks can develop in 1 day (Ghassemi et al., 1983).
 If desiccation cracks  occur, it is necessary to disk and recompact the
 portion of  the Uner that has been affected.  A liner failure documented 1n
 Chapter 7 (Site  I) illustrates the importance of controlling desiccation.

     5.2.2.3.2   Freezing—Liners should not be constructed of frozen soils.
 From the  standpoint of compaction, frozen soils are difficult to work and the
 compactlve  effort needed to achieve a specified density and permeability
 Increases with decreasing temperature, often to the point that the required
 permeability  and  density cannot be achieved.  Thus, 1n colder climates,
 liners cannot be  properly constructed during the winter months.

     Freezing of  a liner can cause surface cracking and degradation of the
 Uner soil  fabric, resulting in increased permeability (Mercuric, Ebasco
Services, Inc., New York, New York, personal communications, 1984).  At the
end  of a construction season,  as well  as at night in the fall  and spring when
temperatures drop below freezing, the liner should be;protected from
freezing.   Liners can be protected from freezing with a blanket of soil  or
organic mulch.

5.2.3  Postlnstallatlon Activities

     Upon completion, the Uner 1s rolled smooth to seal  the surface so that
precipitation and/or leachate  can run freely to the leachate collection
sump.  The  completed Uner 1s  surveyed to ensure that thickness,  slope,  and
surface topography are as required by the design specifications.   Seals
around objects penetrating the Uner (e.g., antiseep collars around leak
detection system pipes) should be checked for Integrity.   The Uner can be
covered with plastic or a soil  cover to prevent desiccation 1f any time will
pass before the next Uner system component (e.g., FML or leachate collection
system) 1s  Installed or before the liner 1s covered with  waste.  This 1s
                                     5-80

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Source: Photo courtesy of Waste Management, Inc., Oakbrook, Illinois       *
             Figure 5-19. Inflatable dome over a hazardous waste landfill.
                                        5-81

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 especially important for bentonite liners or for liners  composed  of  highly
 swelling native soils where desiccation cracking can  occur very quickly.

      For surface impoundments, rip-rap can be placed  on  the upper sidewall
 slopes to protect them from wave erosion.  Experience in dam construction has
 shown that in most cases rip-rap is best placed  by  dumping.  A U.S.  Army
 Corps of Engineers'  survey cited by Small (1981)  found that dumped rip-rap
 failed only 5 percent of the time, whereas the failure rate for hand-placed
 rip-rap was 30 percent.  The failure rate for concrete pavement used as a
 substitute for rip-rap was 36 percent.  Proper sizing of dumped rip-rap is
 critical  to its performance.  Rip-rap slopes  also must be maintained to
 provide reliable liner protection.  Erosion-resistant structures  for
 channeling or loading liquid wastes into surface  impoundments also may be
 constructed after liner installation.

 5.3   QUALITY ASSURANCE AND QUALITY CONTROL

      A recent survey of hazardous  waste  surface  impoundment technology
 revealed  that rigorous construction quality assurance (CQA)  and construc-
 tion  quality control  (CQC)  are necessary to achieve good  site performance
 (Ghassemi  et al.,  1983).   Peirce et al .  (1986) found  a wide variety of
 different  construction and testing methods in  a  survey of 1  German and 22
 ;r4ua!t! J1sP°sa1  facilities.  Liner failures at several  impoundments were
 attributed to various factors  including  "failure to execute proper quality
 assurance  and control."   The success  of  surveyed facilities  that  have per-
 formed  very well  is  attributed to  many factors including  "the use of com-
 petent  design,  construction  and  inspection contractors, close scrutiny of all
 phases  of  design,  construction,  and CQA  inspection by the  owner/operator,
 excellent  CQA and  CQC and recordkeeplng  during all phases  of the  project, and
 good  communications  between  all  parties  involved in establishing  the sites"
 (Ghassemi  et  al.,  1983).   EPA  has  recognized the Importance  of CQA and has
 proposed an  extensive program  for  both new and Interim status hazardous waste
 facilities  (U.S. EPA,  1987).   A  recently developed Technical Guidance Docu-
ment  provides  the  framework  for  the CQA  program required at hazardous waste
 facilities  (U.S. EPA,  1986b).  These  documents should  be consulted for
 specific applications  of  the material discussed in the remainder of this
 section.
mA  ^nHJ1!1 ?auses of Clay I1ner fa11ure that can 4>e avoided with careful
CQA and CQC include:

       t  Use of materials that do not meet the design specifications

       •  Inadequate foundation preparation

       •  Inclusions of roots and other organic matter, large rocks, pockets
          of permeable materials, and other foreign objects 1n the Hner
          material

       •  Inadequate moisture control  both prior to and after compaction

       •  Inadequate clod size reduction,  mixing, and spreading  of Uner
          materials
                                    5-82

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           Emplacement  of  Inadequate amounts of liner materials (especially
           Important  with  bentonite/soil  liners)
        •   Failure  to  follow  installation procedures specified in the design

        •   Use  of improper  or  inadequate construction equipment

        •   Specification or application of inadequate compactive effort

        t   Failure  to  tie lifts together properly

        •   Inadequate  control  of soil moisture content and density during
           compaction  and poor maintenance after construction.

     This  section  specifically addresses quality assurance and quality
control for the construction of clay liners for hazardous waste landfills,
waste piles, and surface Impoundments.  It addresses liners constructed of
both recompacted soil and  bentonlte/soil  admixtures and includes QA
activities that are necessary to ensure that the liner material  1s as
specified and that Installation procedures will  result 1n a liner that will
perform as specified  in the facility design.  This text is a compilation of
information on current CQA and CQC practices obtained 1n the course of this
study through Interviews with design engineers and through literature
reviews.  The section on current practices (Section 5.3.4.4) tabulates much
of the Information obtained during this effort.

     Proper Installation of all of the components of a hazardous waste
storage or disposal unit (I.e., clay liners, synthetic liners, leachate
collecting system,  dikes, and cover systems) 1s  necessary to ensure the
specified performance of the clay liner and the  total  containment system.  As
with clay liners, an adequate CQA and CQC program 1s necessary during
installation of these components to ensure that  they will  perform as
specified; however, a discussion of CQA and CQC  for these components 1s
beyond the scope of this document.

5.3.1  Key Terms

     The following  concepts and terms are used throughout this section.
                                                    8
       •  Construction Quality Management—The process whereby scientific and
          engineering principles and practices are used to ensure that a
          land-based hazardous waste facility 1s constructed 1n  conformance
          with Its  design.   The emphasis  on construction quality management
          must begin as early as possible in the design of the facility, must
          be stressed throughout the actual  construction of the  facility, and
          ceases upon closure of the facility.  Managing construction quality
          is the responsibility of the permit applicant, the construction
          contractor,  and the design engineering firm.   It consists of two
          components,  CQC and CQA.

       •  CQA--A planned series of overview  activities,  the purpose of which
          1s  to provide assurance  that  CQC  1s  being  Implemented  effectively.
          The  system  Involves  a continuing evaluation of the  adequacy and
          effectiveness of  CQC,  the  Inspections  performed,  the data
          collected, and the  Interpretation  of the data made  1n  response  to


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           the CQC activities.  For hazardous waste  land disposal facilities,
           this series of overview activities may  involve verifications,
           audits, and evaluations of the  factors  that affect the Installa-
           tion, Inspection,  and performance of  a  hazardous waste land
           disposal  facility  to ensure that the  facility meets the design
           specifications.

           CQC—Planned and unplanned inspection activities, the purpose
           of which  is to help provide the level of  construction quality
           that will  result in a facility  that meets the design specifica-
           tions.  The overall system involves integrating several related
           factors including:   (1) proper  selection  of specified materials,
           (2) Installation to meet the full intent  of the specification,
           and (3) inspection  to determine whether the resulting product is
           according  to the specification.

           CQA Plan—The CQA  plan that is  discussed  in this chapter  is a
           written approach that may be followed to  attain and maintain
           consistent high quality in the  construction of hazardous waste
           storage and disposal  facilities.  The purpose of a CQA plan 1s
           to ensure  that a completed facility meets or exceeds all design
           criteria.   The CQA  plan is tailored to  the specific facility to
           be constructed and  documents the permit applicant's commitment
           to CQA.
                The CQA plan  1s  prepared as part of  the facility design
           activities.  It is  usually prepared by  the design engineers but in
           some cases may be prepared by an independent third party respon-
           sible for  CQA for the facility.  The  CQA  plan Indicates what tests
           and observations will  be made during  construction to ensure that
           design criteria are met,  as  well as test  frequency and test spacing
           requirements  for CQC.   Acceptance/rejection criteria for specific
           tests are  specified in  the plan and reflect the precision of the
           specific test methods  used and  the specified values, design
           tolerances, and expected  field  variability of the tested param-
           eters.  Also  specified  in  the CQA plan  are corrective actions to be
           implemented if some part  of  the work  is substandard and conse-
           quently rejected.

     While the  overall  content of the CQA plan will  depend on the site-
specific nature  of the  proposed hazardous waste land disposal  facility,  as a
minimum,   several specific elements  should be included in the plan.   These
elements are  summarized  briefly below.

       •  Responsibility and Authority—The responsibility and authority of
          all organizations involved in permitting,  designing,  and construct-
           ing the hazardous waste land disposal  facility  should be  discussed
          fully  in the CQA plan.

       •  CQA and CQC Personnel Qualifications—The  CQA officer,  CQC
          inspector(s), and all other CQA and  CQC personnel  should possess
          the training and experience necessary to fulfill  their identified
          responsibilities, and their qualifications should be presented in
          the CQA plan.
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        •  CQC  Activities  (Observations and Tests)—The specific observations
           and  tests  that  will be used to control or monitor the Installation
           of--the  hazardous waste land disposal facility components should  be
           sufflrasFFfzed In the CQA plan.

        •  Construction Quality Evaluation—The sampling activities,  sample
           size, sample location, frequency of testing, acceptance and rejec-
           tion criteria,  and plans for implementing corrective measures, all
          •thVcQA  Ian 1" the project 5Pec1f1cat1ons, should be presented  in


        •   Documentation—The CQA plan should Include a discussion of the
           reporting  requirements for the project.  This should include  such
           items as daily.summary reports, observation and testing data
           sheets, problem Identification and corrective measures reports
           block evaluation reports, design acceptance reports,  and final
           documentation.   Provisions for the final  storage of all  records
           should also be  discussed  1n the CQA plan.

m , rn? I?ll0?1n9JS a m2re deta1led 11st of important Items to be  Included
IIrS.?2\5iX I°/ddrKs  the above  e1ements Properly.   These  Items have bee
Plan" of SPn8o  !"°2 m%prSvan  J"d !ffect1ve "Contractor Quality  Control
Plan  of ER 1180-1-6 (U.S. Department of the  Army,  1978).  They  are presented
here only as an example and should  not be considered an obligatory or
complete or exclusive outline.   These items are:

       t  A planned  QA organization

       •  An education plan  to ensure that  the workmen, construction manage-
          S?nfh/nrn  ^EeCt2rLare  aware  of the Var1ous ^^^  requirements
          of the project and the reasoning  behind the requirements

       •  Proposed methods for performing CQC Inspections, both for construc-
          tion  process control and  for acceptance sampling and testing (qual-
          ity evaluation); this Includes  Inspections of subcontractors'  work
      *  Name and qualifications of each Individual  assigned a CQA or CQC
         function; method of establishing and verifying personnel  qualifi
         tions to perform specific tests and/or tasks               «""

      •  Discussion of how CQC Inspections will be performed:

              by Inspectors employed by the permit holder designated by
              name, their qualifications, and the specific tests and
              observations to be made

              by subcontract Inspectors designated by name,  their  qualifica
              tions, and the tests and observations  to be made subject to
              approval of the regulatory agency
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        t  The test and/or observation method to  be  used  for  each  specifica-
           tion quality requirement;  whether 1t  1s a standard or alternative
           mefebSiL the reference standard or literature reference  for each;
           the method for establishing size of the unit of  construction  for
           acceptance testing;  the method for establishing  sample  sizes  and
           sampling Locations;  acceptance/rejection  criteria  for each test;
           and the method for dealing with outlying  observations

        •  Location, availability, applicability, and calibration  of test
           facilities and equipment

        •  Procedures for advance notice and coordination of  special
           inspections when and where required

        t  Procedures for reviewing all  drawings, samples,  certificates, or
           other documents for  compliance with permit requirements and for
           certification of their acceptability  to the regulatory  agency;
           qualifications required of the!Individual  performing the reviews

        0  Procedures for reviewing inspection test  results and observation
           records;  qualifications required of individuals  performing the
           reviews

        t  Procedures for observing and  testing fresh exposures of the site
           media (soil  profile)  and for  comparing the results with evaluations
           made during  site characterization studies;  qualifications required
           of  individuals performing  the observations and tests

        •  Action  to be taken by inspectors and reviewers (re:  10, 11, and 12
           above)  when  deficiencies are  identified and/or reported, including
           who  is  to be notified and  in  what manner

        •  Reporting procedures,  providing  for submittal  and/or storage of all
           test and  observation  reports,  at specified  Intervals, and reporting
           of all  actions  taken  under  Item  13  above;  report formats to be used

        •   Definition
-------
      Successful  CQA and CQC requires clarity 1n  written  and  oral  communica-
 tlons among all  the parties,  especially 1n  defining  key  terms and 1n
 delineating ajsas. and lines of authority and responsibility  1n  scope of work
 and other contractual arrangements.   For example,  "inspector,"  "Inspection,"
 "certification," and "verification"  are terms that are used  ubiquitously and
 frequently without regard to  precise definition.  The definitions of these
 terms should be  understood and accepted by  all parties Involved in the clay
 liner project and clearly documented 1n a CQA plan.

 5.3.2.1   Responsibility and Authority—
      The overall  responsibility of the  CQA  and CQC personnel 1s to execute
 activities specified under the CQA plan. As a minimum,  CQA  personnel
 includes a CQA officer and a  CQC inspector.  Specific responsibilities and
 authority of each of these persons are  defined in  the CQA plan  and associated
 contractual  arrangements with the owner. For the  CQA officer,  specific
 responsibilities and areas of authority may include:

       •  Reviewing and fully understanding all  aspects  of the  specified
           landfill  design and proposed  construction  techniques

       «  Serving as the owner's or  design  engineer's liaison with the
           contractor in Interpreting and clarifying  contract documents

       •  Providing CQA reports to the  owner on  the  results of  Inspections
           and testing

       •  Advising  the  owner  or design  engineer  of work  that the  CQA officer-
           believes  should be  corrected,  rejected,  or uncovered  for Inspection
           and of  work that may require  special testing,  inspection, or
           approval

       •  Reviewing  inspection  and test  results  and rejecting defective work
          when authorized to  do so, by the owner  or design engineer

       •  Directing  the CQC inspector 1n performing site Inspections and
          testing

       •  Stopping construction site activities  1n cases where deviations
          from design plans and specifications are defected and Implementing
          corrective actions.

For the CQC Inspector, specific responsibilities  may Include:

       t  Conducting onslte observations and tests of the work  1n progress  to
          assess  compliance by the contractor with the plans, specifications,
          and construction-related contractual provisions for the project

       t   Reporting to the CQA officer results of all  Inspections Including
          work that does not meet the specifications  or  falls to meet
          contract requirements

       •   Monitoring reviews and tests conducted  by the  contractor as
          required by the specifications and contract
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        •  Verifying that tests, equipment»  and system startups  are  conducted
           by .qualified personnel  and proceed according to  standardized
           procedures defined by contract documents.

 5.3.2.2  Qualifications of CQA Personnel-
      Inspectors and CQA officers  should be  trained  1n the  proper use of all
 test methods and equipment.  They should!have the ability  to  calibrate
 equipment,  administer the required tests, record and  interpret  data, and make
 pertinent observations.  The training that  1s required to  obtain these skills
 may come from the classroom or through field experience.   However,  emphasis
 is generally placed on first-hand (field) testing experience.

       In addition to the above requirements,  CQA officers  should be
 registered  professionals who thoroughly understand the theory and application
 of all  physical  and observational  tests, the  overall  site  design, the proper
 use of the  various  types of construction equipment, and project management
 and who have sufficient practical  experience  1n landfill construction.

 5.3.3   Observations and Tests

     This section describes  the observations  and tests that should be
 specified 1n a CQA  plan for  clay  liner  construction.   The  following section
 1s  divided  according  to the  CQA and CQC activities that will take place
 during  preconstructlon,  construction, and postconstructlon periods of clay
 liner  Installation  activities.  All ASTM test methods  referenced 1n this
 chapter may be found  in ASTM (1985).

 5.3.3.1  Reconstruction—
     The first activity under  preconstructlon CQA 1s to review the design
 drawings and construction specifications for  the clay  liner that 1s to be
 Installed with emphasis  on CQA and CQC.  The design drawings and construction
 specifications need  to  be clear and understandable from the standpoint of
 both the onslte CQC  Inspectors and the contractor.  If the design is deemed
 Inadequate  or unclear by the CQA officer, 1t  should be returned to the design
 engineer for clarification and/or modification.

     Prior  to construction,  the CQA officer must also assess the capabilities
 of the  construction contractor's personnel so that he  can determine the type
 and amount  of training,  Instruction, and supervision that will be needed
 during  construction operations.  The contractor's prior performance 1n
 general earthwork activities,  experience In  construction of hazardous waste
 facilities,  and experience 1n working the specific type of soil  and equipment
 to be used  1n constructing the facility in question need to be addressed 1n
this assessment.

     A preconstructlon training plan should  be Included 1n the CQA plan,  as
stated by the U.S. Department of the Army's  Construction Control Manual
 (1977):	—

     Preconstructlon Instructions  and training should be given
     to field Inspection personnel to acquaint them with design
     concepts and to provide them  with a clear understanding of
     expected conditions, methods  of construction,  and the  scope
     of plans and specifications.   This may  be done  by training
     sessions, preferably with design personnel  present,  using a


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      manual of written Instructions prepared especially for field
      personnel, to discuss engineering considerations Involved and
      to explain control procedures and required results.

      If significant quantities of the soil  liner material  are  to be  stored at
 the construction site, the CQA officer should make provisions  to ensure  that
 storage facilities are adequate to prevent  alteration of the liner material.
 For natural clay soils, this could include  seal-rolling, grading, or covering
 the storage pile to encourage runoff and to reduce erosion.  If bentonite/
 soil admixtures are to be used as liner material, 1t 1s critical that benton-
 ite material stored onsite 1s sheltered from precipitation because this
 material cannot be worked except when in a  dry state.

      The CQA plan must provide assurance that any liner material brought onto
 the site is as specified.  Soil  material screening begins  as a preconstruc-
 tion activity and continues during construction as long as material  is being
 brought onsite or excavated from the site.   This activity  can  be accomplished
 in several  ways, depending on the source of the liner material  and site  con-
 ditions.  If the Uner material  1s obtained onsite,  the inspection can be
 accomplished as 1t is placed in  the borrow  pile for  storage.  If the
 excavated soils are heterogeneous, it may be necessary to  segregate  the  soil
 material as 1t 1s excavated, with suitable  soil  placed 1n  a borrow pile  for
 future  use  and son  that  does not meet specifications discarded.  The  CQC
 inspector observes the segregation operations  carefully to ensure that only
 suitable material  1s retained for Uner construction.

      Similarly,  1f the Uner son  1s  obtained  from a  nearby borrow area,
 the son  material  may be  Inspected at the borrow site  or as  the material
 arrives at  the construction site.   Borrow site  Inspection  1s more desirable,
 especially  1f  the  soil  is  heterogeneous,  because  this will  ensure that only
 suitable material  1s transported  to the  site, saving  transportation costs.
 Subsurface  characterization of the borrow site may expedite  this effort for
 heterogeneous  borrow sources.  The U.S.  Department of  the  Navy  (1982)  recom-
 mends that  during  Initial  exploration  of  the borrow pit  area, borings or test
 pits be made on  a  200-foot  grid.   If  variable conditions are found during
 this  Initial exploration,  Intermediate borings or test pits  should be made.
 Borrow  pit  exploration  should produce  the following Information:

        •  A reasonably  accurate subsurface profile do>n  to the anticipated
          excavation depth

        •  Engineering properties of each material considered for use

        •  Approximate volume of each material considered for use

        •  Water  level

        •  Presence of sands, gypsum, or other undesirable materials

        •  Extent of organic or contaminated soils, 1f encountered.

 For extremely heterogeneous borrow areas, 1t may be necessary for  the
 Inspector to guide the excavating equipment to avoid substandard soil
material.
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      Inspection of the soil  can be largely visual;  however,  CQC  personnel
 conducting thjs Inspection must be experienced with visual-manual  soil
 classification techniques (ASTM D 2488).   Changes  1n color or  texture may
 Indicate a charrge 1n soil type or soil  moisture content.  The  soil also may
 be inspected for roots, stumps, and large rocks.  In addition, as  a  check of
 visual  observations, samples of the soil  usually are taken and tested to
 ensure  that the soil's index properties are within  the  range stated  in the
 specifications; tests of moisture/density characteristics (ASTM  D  698) also
 should  be conducted to ensure that these  relationships  do not  change.  The
 number  of tests to be conducted depends on site-specific conditions  (I.e.,
 soil  type and heterogeneity) and the experience of  the  CQC personnel.
 Usually a minimum number of tests per cubic yard of material is  specified,
 with  additional tests required by the inspector 1f  visual observations
 suggest a change 1n soil  type.

      Soil  index properties are simplified tests that provide indirect
 Information about the engineering properties of soils beyond what  can be
 gained  from visual  observations.  Although the correlation between index
 properties and engineering properties is  not perfect, it is  generally
 adequate for CQC purposes.  Index property tests commonly used to  screen
 soils are  described below.

      Atterberg limits include  the liquid  limit and  the  plastic limit (ASTM
 D 4318).   These tests are commonly used along  with  grain size distribution
 for monitoring changes in soil  type.  A significant change in Atterberg
 limits  usually reflects a change 1n  important  engineering properties, such as
 the relationship among moisture content,  density, compactlve effort, and
 permeability.

      Grain  size analysis  1s  another  Important  screening test for changes In
 soil  composition.   The percentage of  clay-size  particles and the overall
 particle size  distribution of  a soil  affects  its engineering properties,
 especially  permeability and  strength.  Rough estimates  of grain size may be
 obtained through manual estimates (ASTM D  2488)  and may be sufficient for
 screening.  A  200-mesh sieve may be used  to  separate  coarse  (sand and gravel)
 and fine (silt and  clay)  particles.   More  detailed  grain size distributions
may be  obtained by  sieving the coarse fraction  and  by using  several settling
methods  (hydrometer,  decantatlon,  or  pipette)  for the fine fraction
 (ASTM D 422).   Cases  where samples of Incoming  or Installed  liner materials
 contain  Inadequate  quantities  of the  necessary  soil particle size may be
 referred to the CQA officer  for evaluation.  Moisture content and consistency
 tests are also needed for screening soils.  Again,  1t 1s Important to monitor
 carefully for  soil  type changes as long as  liner material is being placed.  A
 change  in soil  type  requires the compaction of  another  test  fill  as described
 1n the  following text.

     When bentonite/soll  liners are specified,  Incoming bentonite should be
 Inspected to ensure  that  Its quality  1s as specified.   For all  bentonite
shipments, certification  of  compliance with material  specifications should be
obtained from  the manufacturer or supplier.  In addition, the quality of the
arriving bentonite  should  be tested frequently  for dry  fineness,  pH, and
viscosity and  fluid  loss  of  a  slurry made  from  the bentonite.  Dry fineness
1s the percentage passing  a  200-mesh sieve.  It  1s necessary to control  dry
fineness to ensure proper mixing  of the bentonite.  Slurry viscosity, slurry
fluid loss, and pH are standard  tests specified by the American Petroleum


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                                m , *r -• ,       '"I -  *>
  Institute  (API, 1982).  These tests are necessary to ensure the quality of
  the bentonitejn terms of its swelling potential.  Electric pH meters should
  be used for pJLmeasurements; pH papers are usually not reliable (Xanthakos,
  1979).  If bentonite additives are specified,  the manufacturer's certificate
  contained with each shipment should state compliance with the specified
  characteristics..  More information on testing  bentonite quality may be found
  1n Xanthakos (1979).

      5.3.3.1.1  Test Fill—An important preconstruction CQA activity is to
 determine the suitability of the equipment and methodology to be used to
 compact the liner.  To accomplish this, most design engineers recommend that
 a representative test fill of liner material be compacted with the designated
 equipment to see 1f the specified density/moisture content/permeability
 relationships determined in the laboratory can be achieved 1n the field with
 the compaction equipment to be used and at the specified lift thickness.
 Test fill  dimensions must be sufficient to accommodate the compaction
 equipment.  Several  lifts are usually  compacted  1n the test fill  to check  the
 methodology to be  used to tie lifts together.   The test fill  also is used  to
 determine  the number of equipment passes (or amount of compactlve effort)
 needed to  achieve  the specified permeability and  to determine the ability  of
 mixing equipment to  break up large  clods of uncompacted liner soil.

      Field permeability tests can be conducted on the  compacted  test fill
 material.   Field compactlve  effort  is  different from the  compactlve  effort
 applied in the  laboratory.   Although densities may be  the same for different
 types  of compactlve  efforts,  the  fabric  and the permeability  of  son
 compacted  by  different  methods  can  differ  significantly (Mitchell,  1976).
 These  permeability tests,  therefore, are necessary to  ensure  that  the
 compactlve effort that  1s  applied 1n the field will  result  in the  same  or
 lower  permeability than was  demonstrated 1n the laboratory  tests  of  the  liner
 material.   Additionally,  the  test fill  is  useful  in  establishing  a relation-
 ship between  field permeability and laboratory permeability measurements on
 undisturbed samples  of  compacted  liner material,  which  can  vary by as much as
 3 orders of magnitude  (Day and Daniel,  1985).  The long time  necessary  for
 field  permeability measurements often  limits their use  during construction
 operations  because of scheduling  problems.  However, field  permeability
 measurements  can be  scheduled conveniently  during test  fill compaction.

     In addition to  the number of passes necessary to*achieve the  specified
 permeability, equipment type, size, and compatibility with the soil  type are
 evaluated  and recorded  during test  fill compaction.  Equipment items to be
 checked and recorded include:

       •   For sheepsfoot rollers—drum diameter and  length, empty and
          ballasted weight, length  and face area  of  feet, and the yoking
          arrangement

       •  For rubber-tired rollers—the tire inflation pressure, spacing of
          tires, and empty and ballasted wheel  loads

       t  For vibratory rollers—the static weight,  imparted dynamic force,
          operating frequency of vibration, and the drum diameter and length
          (U.S. Department of the Army, 1977).

This information is necessary to estimate the compactlve effort and
compactlve force applied in the field.

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      Compacting the test fm 1s also valuable 1n that 1t gives  the  CQA
 officer, CQC Inspector, and construction personnel  some experience with  the
 behavior of the specific soils, equipment, and methodology to  be used at the
 site during compaction.  This 1s a very useful base of knowledge to  apply
 when observing compaction of the actual containment facility liner.  The test
 fin compaction thus serves to calibrate ;the Inspectors'  and contractors'
 observations to the conditions that will be encountered during the compaction
 of the liner.

      The successful use of density and moisture content measurements for CQC
 of clay liner compaction depends upon the relationship established among
 density, moisture content, compactive effort,  and permeability for the
 specific soil and for the specific compaction  equipment and methodology  used
 during test fill  compaction.  If a change in son  characteristics or a change
 of compaction equipment or methodology occurs  during liner construction,
 another test fill  should be compacted with the new soil,  equipment,  and/or
 methodology because the original relationships may no longer apply.  If  this
 is not done, there is no assurance that CQC using density/moisture
 content/compactlve effort measurements will  result  1n a Uner  with the
 specified permeability.

 5.3.3.2  Construction—
      An Important  CQC activity during clay liner  installation  1s  observation
 of the construction process,  Including personnel  performance,  by  the
 Inspectors.   Observations by an experienced  inspector,  coupled with a soundly
 developed and implemented CQC testing plan,  will  ensure that the  liner is
 Installed as specified,  that  any potential problems  are identified in a
 timely manner,  and that  proper corrective  actions are  implemented.

      5.3.3.2.1  Foundation  Base Preparation—COG for excavation and construc-
 tion  of foundations  1s  not  fully addressed 1n  this document.  Standard
methods  for  controlling  the quality of foundation preparations and earthen
 embankments may be  found  elsewhere  (e.g., Splgolon and  Kelley,  1984;  U.S.
Department of Interior,  1974;  U.S. Department of the Army, 1977).  The
foundation base must be adequately prepared  before the  clay liner 1s
constructed.  The  natural foundation  should  provide satisfactory contact with
the overlying compacted  Uner, minimize differential settlements  and  thereby
prevent cracking of the  liner, and provide an additional barrier to leachate
migration from  the facility.  To  ensure that these goals are met, observa-
tions during the construction of  foundations should include the following
(U.S. Department of the Army,  1977):

       •  Observations of stripping and excavation to ensure that all soft,
          organic, and otherwise  undesirable materials are removed.   Proof-
          rolling with heavy equipment can be used to detect soft areas
          likely to cause settlement.  Consistency of the foundation  soil may
          be checked with a hand penetrometer,  field vane shear test, or
          similar device.

       •  Inspection of soil and  rock surfaces for adequate filling of  rock
          joints,  clay fractures, or depressions and removal and  filling  of
          sand seams.
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        •  Inspection  of  the  dep|h and slope of the excavation to ensure thai:
           1t  meets  design  requirements.     r   ?

        •  Observations to  ensure proper placement of any recessed areas for
           collection  or  detection pipes and sumps.

        •  Tests  and observations to ensure the quality of compacted fill.

      Visual observation  of the  construction process is the major means of
 ensuring that the foundation is constructed as designed.  Some Instrument
 surveying may be necessary to ensure that facility dimensions, side slopes,
 and  bottom slopes are as specified.  Visual-manual soil identification
 techniques (ASTM D  2488) and index property tests (ASTM D 422; D 4318) may
 be used to monitor  foundation soil composition.

      Soil  consistency may  be checked with a cone penetrometer (ASTM D 3411),,
 This method 1s widely used to determine the consistency of cohesive soils for
 classification and  1s more accurate than the visual-manual method.  It is
 less accurate than  the laboratory method (ASTM D 2166), but can be used to
 give broad consistency classifications for cohesive soils.  Shear strength
 of foundation soils can  be checked 1n the field with a field vane shear
 device  (ASTM  D 2573)  or  a  torvane device (Lanz, 1968).  The ASTM D 2573
 method  is standardized and,  although it Is less accurate, can be correlated
 with the standard laboratory method for unconfirmed compresslve strength
 (ASTM D 2166).  Although all  of these field expedient methods give only
 approximate values, they are usually sufficient for construction.  Compaction
 is controlled as described 1n Section 3.3.3.2.3.

      Further  Information on  quality control of foundations may be found 1n
 Splgolon and  Kelley (1984),  U.S. Department of the Interior (1974), and U.S.
 Department  of the Army (1977).

      5.3.3.2.2  Liner Lift Placement—Liner 11ft placement Includes the
 operation  of  spreading the Uner material(s) over the floor of the facility;
 breaking  and  homogenizing  clods of soil; and, for blended clay liners and
 admixed  liners,  uniformly blending the mixed materials.

      During placement of soil materials, the son  1s spread uniformly as
 specified.  The  loose 11ft thickness of the son  should be measured system-
 atically over  the entire site, with a marked staff or shovel  blade, and
 survey  levels  should be made every few lifts for verification and documenta-
 tion  of  Uner  thickness.  Following spreading,  the Uner material  1s disked
 or tilled to break up large soil aggregates and to homogenize the material.
All   large clods of  liner material  should be reduced 1n size as much as pos-
 sible to facilitate moisture penetration and to ensure uniform compaction
 through the 11ft.  Opinions differ on the  acceptable maximum clod size;  1n
a series of Interviews with design engineers,  recommendations ranged from
 1 Inch to no greater than the 11ft thickness (see  Table 5-11  1n  Section
5.3.3.4).  Close observation by the onslte CQC  Inspector 1s critical  to
ensure that this 1s properly accomplished.

      If bentonlte additives are to be admixed with the natural soil,  the
proper percentage of the additive  must be  controlled.   For spreading and
 1n-place mixing,  this  1s  accomplished by visual  observations  of  the additive
                                    5-93

-------
 as  it  Is spread over the site by hand or by a suitable spreading device.  In
 addition, a spreader can be roughly calibrated by using 1t to spread the
 additive over^a=£!ast1c sheet or pan of given dimensions and then weighing
 the collected material.  Visual observations also should be made to ensure
 that additives are uniformly distributed in each liner lift.  To ensure the
 proper bentonite percentage 1n admixtures, the methylene blue test (see
 Appendix A) can be carried out on representative samples of the admixed
 material.  The soil mixture's liquid limit or plasticity Index has also been
 used to ensure proper bentonite percentage.

      If bentonite additives are to be blended with the native soil prior to
 emplacement, proper bentonite percentage can be ensured by using the
 methylene blue test on samples of the mixed material.  CQC personnel also can
 inspect the mixing operations to ensure that the proper amounts of bentonite
 and soil are placed Into the mixing device and that mixing time and force are
 sufficient.

      5.3.3.2.3  Moisture Control—Moisture content of the liner soil should
 be measured and controlled both before and after 11ft placement to ensure
 that the soil  moisture content 1s as specified and for activating bentonite
 additives.  Nuclear probes (ASTM D317-78) and/or manual moisture content
 measurements are generally used to control moisture 1n the field (see
 Chapter 3).  The following description of manual moisture estimation is
 adapted from Johnson et al. (1983).

      In order for quality control  personnel to satisfactorily estimate fill
      water contents, they must become thoroughly familiar with the fill
      material  prior to the start of fill  operations.  Preferably, they should
      spend some time in the field laboratory, performing several  compaction
      tests to become familiar with the differences 1n appearance and behavior
      of the various fill  materials, to recognize when they are too dry or too
      wet,  as well  as when they are at the specified water content.
      Inspection personnel  should also run several  Atterberg limits on
      fine-grained  soils so they can compare the appearance and feel  of the
      soils  when they are  at the plastic limit with that at proper water
      content for compaction.

      Trained personnel  should  then  be able to pick up a handful  of soil  and
     make a  reasonable  estimate of  the relation  of Its water  content to Its
      optimum water  content  by  feel  and appearance  (experienced technicians
      often  can  estimate deviation of  water content from optimum within  +1
     percent).   Occasional  moisture tests  should be  made  to confirm  these
     manual  estimates.

A few reference  bags of liner material at  known moisture  contents  stored at
the  site can be  very helpful for calibration  of manual moisture content
estimates.

     Many design engineers  recommend that oven moisture content measurements
by the appropriate test method  (ASTM D2216-80) be taken at  Intervals to
ensure that nuclear measurements and manual estimates are accurate.  Proper-
moisture content is achieved and maintained with sprinkling devices  (1f too
dry) or by a combination of mechanical agitation, aeration, and solar drying
(1f too wet).
                                    5-94

-------
      If the liner 1s to be left exposed between the Installation of succes-
 sive lifts or^after completion, the QC personnel  make sure that 1t  1s
 protected from moisture content^.change by ensuring that seal-rolling 1s
 uniformly performed over the site and that cover  material, 1f used,  1s
 properly emplaced.  If desiccation does occur,  the QC inspector reports  this
 to the QA officer, who notes this and specifies remedial  actions, such as
 disking and recompactlon of the affected portion  of the liner.

      5.3.3.2.4  Compaction—Son  selection based  on laboratory  compaction and
 permeability tests is made on samples of the liner material  during  design of
 the facility.   A relationship among moisture contents,  densities, and
 permeabilities is established based on test results.   Design  specifications
 usually require achievement of a minimum percentage of the maximum  density
 (Proctor or modified Proctor) at a specified range of water contents, based
 on these results.  The specified density/water  content corresponds  to the
 density/water  content at which the specified permeability can be achieved as
 established by the laboratory and test fill  compaction tests.  This  density/
 water content  1s then tested during quality control  of clay Uner
 installation.

      Additionally, during compaction of each lift, compactlve effort and
 uniformity of  compaction are observed and recorded.   Compactlve effort 1s
 estimated by the number of passes of equipment  of a known size  and weight.
 It is important to make coverage uniform, especially  at fill  edges  and 1n
 equipment turnaround areas and at the top and bottom  of slopes  (Spigolon and
 Kelley, 1984),  In addition,  permeability tests often are conducted
 periodically on the compacted liner material  as a check on the  moisture/
 density/permeability relationship.  It 1s generally agreed that all  of the
 above measurements are necessary to ensure that the  specified permeability
 1s being achieved in the field.  Density measurement  should never be used
 alone for quality control  of  clay Uner Installation.

      The relationship among moisture content, density,  compactlve effort, and
 permeability is unique for a  specific soil  or soil mixture and  specific  type
 of equipment.   Laboratory compaction tests to establish density/moisture
 curves  are  determined regularly on field samples  of the clay  Uner to
 determine  changes 1n optimum  water contents.  If  these  tests  or field
 Inspection  of  the Incoming  Uner  materials Indicate a significant change,
 laboratory  permeability tests and a  test fill compact-Ion must be conducted to
 establish the  density,  moisture,  and permeability  relationship  for the new
 soil.   Otherwise,  attainment  of the  moisture/density  relationship that was
 specified for  the original  soil may  result 1n an unacceptable permeability
with  the new soil.   Similarly,  1f different compaction equipment or
methodology 1s  used, another  test  fill  should be compacted with the new
equipment because  the  type  of  compactlve effort applied affects the final
permeability.

     The design engineers Interviewed during this Investigation stressed  the
Importance of visual and manual observations by a qualified Inspector for
Uner compaction quality control.  Some consider specific tests only a backup
documentation to observations by the qualified CQC Inspector.  All
professionals interviewed agreed that observation  of the construction process
1s the primary  and most effective approach to CQC.  Testing 1s secondary;
beyond the minimum test frequency and spacing, visual  observations are used
                                    5-95

-------
 to Identify problem areas and to call for more Intensive testing to document
 and delineate_any substandard liner areas.  Remedial  actions  (e.g., removal
 and reconstruction) are then ordered for the substandard areas  so
 delineated.  All engineers stressed the Importance of having  a  qualified
 Inspector on the site at all times during construction.

      An experienced observer can determine how compaction 1s  proceeding
 (e.g., moisture content and density) by observing how the equipment moves
 across the area to be compacted, how the soil  contacts or sticks to the
 compaction equipment, how the soil heaves during compaction,  how deep  the
 compaction equipment sinks into the soil, and  how the roller  walks  out of  the
 soil  (sheepsfoot rollers only) (Johnson et al., 1983).  In addition, it  is
 Important to observe uniformity of coverage by compaction equipment,
 especially at fill edges, in equipment turnaround areas, and  at the top and
 bottom of slopes (Splgolon and Kelley, 1984).

      5.3.3.2.5  Specific Tests—Testing and sampling  of  the liner are
 necessary to ensure compliance with the design requirements and to  document
 the as-built conditions of the clay liner.  Specific  tests to ensure that
 compaction results 1n the specified liner permeability Include  field density
 tests (nuclear, sand-cone, and others), field  moisture content  measurements,
 laboratory compaction tests, and both field and laboratory permeability
 tests.  The methods and QC measures for conducting these tests  may  be  found
 1n  several  documents (MSHTO, 1978; ASTM, 1985; U.S.  Department of  the Army,
 1970;  and U.S. Department of the Interior, 1974)  and  are briefly discussed in
 Chapter 3 and Appendix A.  The main tools used for controlling  the  quality of
 compaction are field density and moisture content measurements,  with supple-
 mentary laboratory compaction tests providing  a means of monitoring  changes
 1n  soil  material.   A laboratory compaction test should be conducted  for every
 10  to  20 field density/moisture determinations, depending on  soil variability
 (U.S.  Department of the Navy,  1982).   Nuclear  probes  may be used  to  measure
 field  density and  moisture content,  but these  must be calibrated  for each
 soil  that 1s  to be tested.  In  addition,  if  nuclear devices are  used,  other
 field  density and  moisture content  measurements,  such as  sand cones  and oven
 drying,  should be  made periodically to  confirm nuclear results.  Again, 1t
 1s  necessary  to measure density, moisture, and  compactlve  effort  1n  the
 field  to  ensure that .the required permeability  1s  achieved during clay liner
 compaction.
                                                     0
     In addition to density and moisture measurements  and  estimates of
 compactlve effort, permeability tests should be made  regularly to confirm
 that the measured moisture/density  levels  correspond  to those required for
 the specified  permeabilities.  Shelby tube or block samples may be taken  for
 laboratory permeability tests  (ASTM D 1587-74; ASTM,  1985), or field
 permeability tests may  be  performed.  Laboratory permeability tests are
 easy to conduct, do not  consume valuable construction  time, and are quicker
 than some field permeability tests.  However, they  can underestimate field
 permeability by as much  as 3 orders of magnitude  (Day and Daniel, 1985).
 Field permeability tests more accurately represent actual permeabilities,  but
 some can take many days  to complete, seriously Interrupting construction
activities.  Field permeability tests may be conducted on test fills prior to
 construction so that construction activities will not be  Interrupted.  (For
further discussion of field versus  laboratory permeability measurements and
for a discussion of test methods, see Daniel, 1981; Olson and  Daniel, 1981;
                                    5-96

-------
 Rogowski and Richie, 1984;  and Daniel,  1987;  also  see  Chapter  3  of  this
 document.)
      Several -d^Kjn engineers reeooimended  that moisture/density measurements
 and Shelby tube samples for laboratory permeability  tests be obtained from
 the 11ft underlying the lift that  has  just been  compacted.  These engineers
 believe that during compaction of  a  lift,  significant  compactlve effort is
 being applied  to the underlying lift.   A more accurate representation of the
 degree of compaction across the liner  is achieved by testing the underlying
 1 1 T t •

      Following Shelby tube  sampling, nuclear density measurements, or field
 permeability testing, the resulting  hole is filled with  liner material and
 hand tamped or is grouted, with bentonlte.   Over  excavation of the hole with a
 shovel  to slope the sides of the hole  prior to backfilling may further
 facilitate sealing.  Test locations  should be staggered  from lift to 11ft so
 that the testing or sampling holes. do  not  line up.   This also gives better
 test coverage  of the liner.

      Index property tests (e.g., grain size, clay content, and Atterberg
 limits)  are used to evaluate liner soils prior to emplacement in order to
 monitor changes in soil  type.  These test  methods are  well established and
 are described  1n Chapter 3  and in  Appendix A.

      Minimum test frequency and test spacing should  be specified for all
 tests in the test plan.   Test spacing  practices  and  frequency are discussed
 in  Section 5.3.3.4 of this  report.

 5.3.3.3   Completion Tests--
      Upon completion of  the liner, CQA personnel should  check that it is
 rolled  smooth  to seal  the surface  so that  precipitation and/or leachate can
 run freely to  the leachate  collection  sump.  The completed liner should be
 surveyed to ensure that  thickness, slope,  and surface  topography are as
 required by the design specifications.  Seals around objects penetrating the
 Uner (e.g., leak detection system stand pipes) also should be checked for
 integrity.

      Field  permeability  tests  should be conducted on the completed Uner as a
 final QA check.   It  appears  that field measurements o£ permeability (e.g.,
with  sealed double  ring  inflltrometers) are preferable to laboratory measure-
ments because  they  subject  a  larger portion of the Uner to permeability
 testing.  Recent work has shown  that field permeability measurements yield an
average  hydraulic  conductivity close to a  liner's actual hydraulic conductiv-
 ity.  Laboratory tests, even on undisturbed samples, can give a hydraulic
conductivity 19000 times  less than the actual  value, measured by collecting
seepage  through the  Uner (Day and Daniel,  1985).  Several  field permeameters
can be set up over the site, or 1f the site 1s  not too large or 1s a surface
impoundment the facility can be filled with water and seepage from the site
can be measured after accounting for evaporation.  The latter method,  when
feasible, ensures that the entire site will function according  to specifica-
tions once 1t  is filled, assuming that no waste/ liner compatibility problems
occur.
                                    5-97

-------
       If the  completed  Uner  1s  to be  left exposed prior to Installation of
  the overlying, facility components, CQC Inspectors should ensure that the
  Uner 1s covered adequately  with soil or plastic sheeting to prevent
  desiccation  aiRTwind erosion or that  1t 1s maintained at suitable moisture
  content by managed water application.

  5.3.3.4  Current Sampling Program Design Practices--
       Current CQC practice relies on the Inspector's observations and judgment
  for accepting most of  the work, with actual  sampling and testing of the
 material  serving only  to document compliance and to help guide the Inspec-
  tor s judgment.  Table 5-11  is a summary of information on current CQC
 practices obtained during Interviews with design engineers active 1n desiqn-
  ing and  controlling the construction quality of clay liners.   Also Included
  in this  table is information from earthwork  construction manuals of the U.S.
 Department of the Interior and the U.S. Department of the Navy.  Tables 5-12
 and 5-13  11st recommendations for construction documentation  recently
 published by the Wisconsin Department of Natural Resources personnel.

      Statistical sampling methods for earthwork quality control (geostatls-
 tics) have been developed by the U.S. Department of the Interior and the "
 U.S. Army Corps of Engineers (U.S.  Department of the Interior,  1974; U.S.
 Department of the Army, 1977; Davis,  1966; Turnbull  et al.,  1966;
 Wlllenbrpck,  1976).  These documents  Include statistical  methodology to
 eft??1lfh de9re? of confidence for a  testing program.  Other  discussions of
 statistical  methods may be found 1n Wlnterkorn and Fang (1975), Sellg (19821
 Wahls et al.  (1968), Jorgenson (1971), and Kotzlas and Stamatapoulous
 (1975) «


 n™ £l9ures  ?720 ^JL5"?1 11lustrate a simple, concise method  of  documenta-
 tion of clay Uner CQC  statistics developed  by Soil  Testing Engineers of
 Baton Rouge,  Louisiana.  Figure 5-20  Illustrates the sampling locations for
 f?nne^%Sf  a ^""/U^ ]?nf 111  cfil ' •   "«"« 5-21 is a  graphic  presenta-
  1 ^°!,the mo1sture/dens1ty/permeab1l1ty data and clearly Illustrates  the
 statistical analyses performed on  these data.   These figures  are presented as
 examples of good CQC documentation  and statistical  analysis.

 5.3.4  Documentation
                  ,.J      dePends  heavily on  recogn1«1ng all construction
            that  should  be  Inspected and assigning responsibilities to CQA and
 CQC  personnel  for Inspecting  each activity.  This 1s most effectively
 accomplished by  documenting CQA and CQC activities and should be addressed as
 the  fifth element of  the CQA  plan.  CQC personnel will be reminded of the
 factors to  be  Inspected and will note by signing required descriptive
 remarks, data  sheets, and  checklists that , the  Inspection activity has been
 accomplished.

 5.3.4.1  Daily Recordkeeplng—
     Standard dally reporting procedures should Include preparation of a
 summary report with data sheets for supporting observation and testing and,
when appropriate, for problem identification and corrective measures.

 ..   5.3.4.1.1  Daily Summary Report— A summary report, or project Inspection
diary, should be prepared dally by the CQA officer.   This report provides  the
                                    5-98

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                                                                  TABLE 5-11.   CURRENT  QA  PRACTICES FOR CLAY LINEK CONSTRUCTION
CO
to
Source of
information3
A


B


C
D

E

F
G


H

Minimum frequency of
in-place moisture or
density tests
1 per 1,000 yd3 of fill


Moisture tests only (used
with permeability tests
and compact! ve effort to
control compaction)
Frequency per unit volume
of fill based on experience
1 per 2,500 ft2 of lift

Frequency, per unit volume
of fill, based on experience
and liner material
homogenei ty
Statistical approach
9 per acre of lift


1 per 2,000 ft2 or at least
1 per lift

Permeability testing
Occasional lab test


Trlaxial and some field tests


Lab tests
Triaxlal--! per 3 acre feet
with minimum of 1 per acre

Modified trlaxial, fixed-wall,
and consolidation lab tests—
per unit volume of fill.
based on experience
Lab tests— 5 to 6 per acre
Falling head field test at
density test location— 1 per
acre of lift
Lab test-1 per 10,000 to
20.000 ft2 or every third
lift
Sample or
test hole Test fill
filling method recommended
Mot usually


Bentonite Yes


—
Liner material Yes
hand-tamped

-

Yes
Yes


Liner material
or bentonite
hand- tamped
Maximum clod size
allowed
1/2 lift' thickness; none
greater than lift
thickness
2 inches


1/2 lift thickness
1/2 lift thickness, if
possible; none greater
than lift thickness
-

	



1 inch in upper lifts;
may be larger in lower
lifts
Maximum rock or
root size allowed

1

2 inches


-
4 to 6 inches

3 to 6 inches or
1/2 lift thickness





1 inch .
' <

                                                                                                                                                                       (continued)

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                                                                                TABLE 5-11.  (continued)
ui
o
o
Source of
information3
I


J




K


HlniBun frequency of
In-place Moisture or
density tests
1 per 2,500 ft? aininua
of 4 per lift or 1 per
day— More as needed

1 per 10,000 ft? or 1 per
1 1 It



Site specific, based on
experience


Permeability testing
Laboratory test— 1 per 2,000
yd3 or 2 per lift— occasional
field test

Lab and field




Lab trl axial


Sample or
test hole
filling method
Bentonite


—




Bentonite


Test fill
recontended
Yes


Yes




Sometimes,
especially
for admix-
tures
Maximum clod size
allowed
1/2 lift thickness


1/2 lift thickness if
possible; none greater
than lift thickness;
1 to 3 Inches for hand-
compacted areas
3 to 6 inches, depending
on compaction equipment;
1 inch In upper 1 foot
of liner If overlain by
Max i num rock or
root size allowed
-

II





1 inch


                                                                                                                               FML; none greater than
                                                                                                                               lift thickness
L           1 per 1,000 yd3 or 1  per
            day

M           1 per 1,000 yd3 or 1  per
            day

Nd          1 per 1,000 yd3—! per 200
            yd3 if hand tanped
Lab constant  head—1 per 25.000
yd3 or 1 per  week

Lab falling head—1 per
25,000 yd3
Yes


No


Yes
                                                                                                                               3 inches;  3/4 inch for
                                                                                                                               blended materials
             'Sources A through H were design and geotechnical engineers with clay liner construction experience.
             DU.S. Bureau of Reclamation,  1974.       .
             <-U.S. Department of the  Navy,  1982.     *
             "Ghasseni  et al.,  1983.
                                                                                                3 Inches
Oc 1 per 500 to 1,000 yd3

Pd 1 per 2,000 yd3

3 inches; 1 to 3 Inches
for hand-compacted areas
Lab— 1 per 16,000 yd3, field— — — 3 to 6 Inches
1 per 40,000 yd3

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    TABLE 5-12.  RECOMMENDATIONS FOR CONSTRUCTION DOCUMENTATION  OF  CLAY-LINED
           LANDFILLS BY THE WISCONSIN DEPARTMENT OF  NATURAL  RESOURCES
           Item
                                      Testing
                                   Frequency
  1.   Clay  borrow source
      testing
 2.  Clay Uner testing
     during construction
3.   Granular drainage
     blanket testing
 Grain size
 Moisture content

 Atterberg limits
 (liquid limit and
 plasticity index)

 Moisture-density curve


 Lab permeability
 (remolded samples)

 Density
 (nuclear or sand cone)

 Moisture content
                             Undisturbed permeability
Dry density
(undisturbed sample)

Moisture content
(undisturbed sample)

Atterberg limits
(liquid limit and
plasticity index)

Grain size (to the
2-m1cron particle size)

Moisture-density curve
(as per clay borrow
requirements)

Grain size
(to the No. 200 sieve)

Permeability
 1,000 yd3


 1,000 yd3

 5,000 yd3
                                                          5,000 yd3 and all
                                                          changes in material

                                                          10,000 yd3
5 tests/acre/lift
(250 yd3)

5 tests/acre/lift
(250 yd3)

1 test/acre/lift
(1,500 yd3)

1 test/acre/lift
(1,500 yd3)

1 test/acre/lift
(1,500 yd3)

1 test/acre/lift
(1,500 yd3)
                                                           1 test/acre/lift
                                                           (1,500 yd3)

                                                           5,000 yd3 and all
                                                           changes 1n material
 1,500 yd3


 3,000 yd3
Source:  Gordon et al., 1984.
                                    5-101

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         TABLE 5-13.  ELEMENTS OF A CONSTRUCTION  DOCUMENTATION REPORT
         Major—etements
              Components
 A.  Engineering plans
Completed sub-base elevations.

Final clay Uner grades.

Top of drainage blanket grades.

Leachate collection lines, cleanouts,
and manholes with spot elevation every
100 feet along the lines and at all
manhole entrances and exits.

Drainage features.

All monitoring devices.

Spot elevations at all breaks In slope
and on approximate 100-foot centers.

Document testing locations.

Other site information as appropriate.
B.   Engineering  cross-sections
C.  Comprehensive  narrative
D.  Series of 35-mm color prints
E.  Construction certification
Minimum of one east-west and one
north-south through the completed
area.

Explaining how construction of the
project was accomplished along with an
analysis of the soil-testing data
obtained in 1 through 3 above.  This
report should also include an appendix
containing all the raw data from the
field and laboratory testing.

Documenting all major aspects of site
construction.

Should be certified by a registered
professional  engineer to have been
completed according to the approved
plans.  Any deviations from the plans
should be noted and explained.
Source:  Gordon et al., 1984.
                                     5-102

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ELEVATION POINTS « »'jj ij']i »j
SUITS
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Licur IhickMtioi givin for poinli oo llopn on \\ ,l'" ]!'!? !1
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LINER THICKNESS DATA
SUMMARY of RESULTS
THICKNESS DATA- ATTERBERG LIMIT DETERMINATIONS'-
Number of data points - 49 »» Number of t«"i M 30
Average thickness value, 5.5 Av*"|J «""•' . 5g
Standard deviation » 0.7 ft. *H- ^ ^
plasticity mdex * 40
Standard deviation!
COMPACTION DATA: liquid limit » 13
Number of tests .148 plasticity mdex - 17
Average compaction, 9I% PERMEAB1L|TY TESTS:
Number of tests • 14

PERMITTING STUDY
•

I SOL INVE3TOA710H SI
A^OL [ESINGENGMEERS, INC.
II IV 1 CM 1 JPMMIM
I DOW 1 SJC 1 [ Q-2A
1 1 1 1

       Source: Courtesy of Soil Testing Engineers, Inc., Baton Rouge, Louisiana
                                                     Figure 5-20. CQC test location and data summary.

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U1
 i

to
»0
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                                                       Figure 5-21. Statistical analysis of CQC test data.

-------
 chronologic framework for identifying  and  recording all other  reports.  At a
 minimum,  the jummary reports  should  include  the  following  information
 (Spigolon andJ£e_Lley, 1984):       ;            #

        •   Unique identifying  sheet number  for  cross-referencing and document
           control

        •   Date,  project  name,  location, and  other  identification

        •   Data on weather conditions

        •   Reports on any meetings  held and their results

        •   Unit processes,  and  locations, of  construction underway during the
           time frame of  the report

        t   Equipment  and  personnel  in each unit process, including
           subcontractors

        •   Descriptions of  areas or units of work (blocks) tested and/or
           observed and documented

        •   Description of offsite materials received, including any quality
           verification (vendor certification) documentation

        •   Calibrations,  or recallbratlons, of test equipment, Including
           actions taken  as a result of recallbration

        •   Decisions  made regarding approval of units of material or of work
           (blocks) and/or  corrective actions to be taken 1n Instances of
           substandard quality

        t   Unique identifying sheet numbers of observation and testing data
           sheets and/or  problem reporting and corrective measures data sheets
           used to substantiate decisions described In the preceding item

        •   Signature  of the CQC Inspector and concurrence by the CQA officer.

     Items above may be  formulated Into site-specific^checklists and data
sheets  so  that details are not overlooked.

     5.3.4.1.2  Observation and Testing Data Sheets—All observations and
field and/or laboratory  tests should be recorded on appropriate data sheets.
Required data to be  Included 1n a  test report (data sheet) for most of the
standardized test methods are included 1n the pertinent ASSHTO (1983) and
ASTM (1985) standards.   Examples of field and/or laboratory test data sheets
are given  1n U.S. Department of the Army (1970, 1978) manuals and 1n Spigolon
and Kelley (1984).

     Due to their nonspecific nature, no standard format can be given for
data sheets to record observations.  Recorded observations may take the form
of notes,  charts, sketches, photographs, or any combination of these.  Where
possible,  a checklist may be useful to ensure that no pertinent factors of a
task-specific observation are overlooked.
                                    5-105

-------
      Observation and testing data sheets should  Include  at  least  the
 following Information (Splgolon and Kelly,  1984):
        •  Unique Identifying sheet number for cross-referencing and document
           control
        •  Description or title of the  observation/test
        t  Location of the observation/test  or location from which the sample
           Increment was  obtained
        •  Type  of  observation/test;  procedure used  (reference to standard
           method when appropriate)
        •  Recorded observations  or  test  data, with all necessary calculations
        •  Results  of the  observation/test;  comparison with specification
           requirements
        •  Personnel  Involved 1n  the  observation/test
        •  Signature  of the CQC Inspector and  concurrence by the CQA officer.
Items above may be formulated into site-specific checklists and data sheets
so that  details are  not overlooked.
cu  ^5'3:4^*3  Problem Identification and Corrective Measures Data
Sheets—Problem reporting ana corrective measures data sheets  should be
nrnh?Ime!!ce?S!dfJ«S58C1J!C Obfervat1on or testing data sheets where  the
problem was Identified.  They should, at a minimum, Include the following
information:                                                            a
       •  Unique Identifying sheet number for cross-referencing and  document
          control
       t  Detailed description of the problem
       •  Location of the problem
                                                     «
       •  Probable cause
       t  Method and time frame of locating  the problem  (reference to  data
          sheets)
       •  Estimated duration of the problem
       •  Suggested corrective  action
       •  Documentation of correction (reference  to data  sheet)
       •  Final  results
       •  Suggested methods  to  prevent  similar problems
          Signature of the CQC  inspector  and concurrence by the CQA officer.

                                   5-106
a

-------
 In some cases, not all of the above information wm  be available  or
 obtainable.  However, when available, such efforts to document  problems  could
 help to avoid-similar future problems.

      The CQA officer should be made aware of any significant  recurring
 nonconformances.  The CQA officer will then determine the  cause of any
 problems and recommend appropriate changes to prevent future  recurrence.
 When this type of evaluation 1s made, the results should be documented.

      Upon receiving the CQA officer's written concurrence, copies  of the
 report(s) should be sent to the design engineer and the facility owner/
 operator for their comments and/or acceptance.   These reports should not be
 submitted to the permitting agency unless they  have been specifically
 requested.  However,  a summary of the data sheets along with final testing
 results  and inspector certification of the facility may be required  by the
 permitting agency upon completion of construction.

 5.3.4.2   Photographic Reporting Data Sheets--
      Photographic reporting data sheets may also  prove  useful.   Such data
 sheets should  be cross-referenced with observations or  testing  data  sheets
 and/or problem identification  and corrective measures data sheets.
 Photographic reporting data sheets should include  the following minimum
 information:

       t   A unique  identifying  number  for cross-referencing and document
           control

       t   The  date, location,  and weather conditions  for the photograph

       t   Location  and description of  the work or work  product

       •   Purpose of  the photograph

       t   Signature of the  photographer and  CQC Inspector.

 These photographs will  serve as  a  pictorial  record of work progress,
 problems,  and mitigation activities.   They  should be kept in plastic file
 sheets in  the  chronological order  in which  they were taken.  The basic file
 should contain color  prints; negatives should be  stored  1n a separate file 1n
 chronological order.

     A video recording  of problem  areas and/or conditions and of the
 completed  Installation  of each  soil  component may also prove useful.

 5.3.4.3  Block Evaluation Reports-
     Each  Inspection  block may have  several quality characteristics, or
 parameters, that are  specified to  be observed or tested, each by a different
 observation or test, with the observations and/or tests recorded on different
data sheets.  At the  completion of each block, these data sheets should be
organized Into a block evaluation  report.  These block evaluation reports may
then be used to summarize all of the site construction activities.
                                    5-107

-------
      Block evaluation reports should be prepared by the CQA officer  and, at a
 minimum, shouJd Include the following Information (Splgolon and  Kelley,
 1984)t        -.

        •  Unique Identifying sheet number for cross-referencing  and  document
           control

        0  Description of block (use project coordinate system to Identify
           areas and appropriate identifiers for other units of materials or
           work)

        •  Quality characteristic being evaluated; references to  sections of
           specifications

        •  Sampling method; how 1t was established

        •  Sample increment locations (describe by project  coordinates  or by a
           location sketch on the reverse of the sheet)

        •  Tests and/or observations made (define procedure by name or  other
           identifier; give unique identifying sheet number for observation
           test data sheets)

        t  Summary  of test data (give block  average  and,  1f available,  the
           standard deviation for each quality characteristic)

        •  Define acceptance  criteria (compare block observation/test data
           with design specification requirements;  indicate compliance  or
           noncompllance;  1n  the  event of noncompliance,  Identify documenta-
           tion that gives reasons  for acceptance  without specification
           compliance)

        t  Signature of the CQA officer.

5.3.4.4 Design  Engineer's Acceptance  of Completed  Components--
     All daily inspection  summary  reports, observation and testing data
sheets,  problem  identification and  corrective measures sheets, and block
evaluation reports  should be  reviewed  by the CQA officer and then submitted
to the  design  engineer.  The  reports  should be evaluated and analyzed for
Internal consistency and  for  consistency with similar work.  Timely
submission of  these documents will  permit errors, inconsistencies, and other
problems to be detected and corrected as  they occur, when corrective measures
are easiest.

     The design engineer  should assemble and summarize the above information
Into a  periodic design acceptance  report.  The reports should indicate that
the materials and workmanship comply with design specifications and permit
requirements.  These reports  should be Included 1n project records and, 1f
requested, submitted to the permitting agency.

5.3.4.5  Final Documentation—
     At the completion of the project, the facility owner/operator should
submit a final documentation  report to the permitting agency.  This report
should Include all  of the design engineer's acceptance reports (I.e.,
                                    5-108

-------
 periodic summaries of all  dally Inspection  summary  reports, observation and
 test data shejts,  problem  Identification and corrective measures data sheets,
 and block evaluation  reports),  deviations from design and material specifica-
 tions (with justfylng documentation), and as-built  drawings.  This document
 should be prepared by the  CQA officer and Included  as part of the CQA plan
 documentation.

      5.3.4.5.1   Responsibility  and Authority—The final documentation should
 reemphaslze that areas of  responsibility and lines  of authority were clearly
 defined, understood,  and accepted by all parties involved 1n the project.
 Signatures of the  facility owner/operator,  design engineer, CQA officer, CQC
 inspector, and  construction contractor  should be included as confirmation
 that each party understood and  accepted the areas of responsibility and lines
 of authority and performed their function(s) according to the CQA plan.

      5.3.4.5.2   Relationship to Permitting  Agencies—Final documentation
 submitted to the permitting agency as part  of the CQA plan documentation does
 not sanction the CQA  plan  as a  guarantee of facility construction and
 performance. Rather,  the  primary purpose of the final documentation is to
 improve  confidence 1n  the  constructed facility through written evidence that;
 the CQA  plan was Implemented as proposed and that the construction proceeded
 according to design plans  and specifications.

 5.3.4.6   Storage of Records—
      During  the construction of a hazardous waste land disposal facility, the
 CQA officer  should be  responsible for the facility  records, including the
 originals of all the data  sheets, summary reports,  and block evaluation
 reports;  the design engineer's  acceptance of completed components reports;
 and facility drawings.  With the CQA officer 1n charge of the facility
 construction records,  any  documentation problems should be noted and
 therefore remediated quickly.   Once the facility construction 1s complete,
 the document originals  should be stored by the owner/operator 1n a manner
 that will  allow for easy access.  An additional copy should also be kept at
 the facility if this 1s 1n  a different  location from the owner/operator's
 files.  A final   copy should be  kept by  the permitting agency 1n a publicly
acknowledged  repository.

5.4  CLAY  LINER  DESIGN AND  CONSTRUCTION:  PROBLEMS AND PREVENTIVE MEASURES
                                                     *
     Table 5-14  lists common problems encountered during clay liner design
and  construction,  their probable causes, and suggested solutions.  This table
was  compiled from  Information assembled from a wide variety of sources,
including  literature surveys, case studies,  and Interviews with experts 1n
the  field.  This table summarizes Information presented 1n this chapter.
                                    5-109

-------
                                     TABLE  5-14.   POTENTIAL  CLAY  LINER DESIGN AMD INSTALLATION PROBLEMS AMD PREVENTIVE MEASURES
                                      Problems
                                                                       Cause
                                                                                                      Preventive measures
                             Sidewall  slump  and collapse
    Improper  characterization
    of soil strength profile
    that  results  in inproper
    sidewall  design.
    High  inward hydraulic
    pressure  on sidewalls
    (sites below  water table).
                            bottom heave or rupture
o  High inward hydraulic
   pressure on bottom
   (sites below water table).
01
i
                            Accumulation of water in      •  Rainfall
                            landfill during construction
                                                             Seepage into site
                                                             (sites below water table)
                            Drying and cracking of clay
                            liner, greatly increasing
                            permeability
•  Desiccation
 •  Properly characterize subsurface  condi-
    tions.
 t  Design a more gentle  sidewall  slope
    (depending  on shear strength
    of foundation soil.)
 •  Reduce hydraulic  head  by:
    —  Installing slurry  wall  around  site
        perimeter to  cut off  groundwater.
    —  Trenching and pumping around site
        to cut  off groundwater.
    —  Pumping from  wells to lower local
        groundwater table.

 •  Control  depth of  excavation to
    lower  head  potential.
 •  Reduce hydraulic.head  by  slurry
    wall,  pumping,  or other technique.
    Fill landfill  before heaving occurs.

 •  Cover  site  with inflatable dome (re-
    duces  leachate treatment  requirements
    for  continuous  operation  facilities).
 •  Seal roll liner at end of construc-
    tion day  to ensure proper runoff of
    precipitation into .sump.

 •  Reduce hydraulic  head  in  surrounding soil.

 •  For  all  infiltration:
    —  Operate leachate collection
       system  to remove water.
    --  Design  leachate collection system
       or detection  system (between liners)
       to handle extra water input.

t   Do not construct during extremely
    hot, dry periods.
•   Wet down liner  during  dry periods.
•   Cover  liner with plastic sheet or
    soil layer if liner construction  is
    interrupted.
9  Do not leave  liner exposed prior  to
   waste emplacement or leachate collection
   system installation.
                                                                                                                          (continued)

-------
                                                                       TAULE b-14  (continued)
ui
                                       Problems
                                                                      Cause
                                                                                                     Preventive measures
                             Loss in liner density
                             (increased permeability)
                               •  Freeze/thaw
                             Reduction in clay workability  •  Low temperatures
Erosion of upper liner after
construction
(liquid impoundments)

Visible partings between
liner lifts and increased
permeability parallel to
lifts

Pockets of high-permeability
material (e.g., sand and
gravel) in liner material
                            Leakage around designed
                            liner penetrations

                            Leachate collection
                            system clogging

                            Leachate collection syatein
                            damage during waste
                            emplacement
                                                           •  Wave erosion
                                                              Liner lifts not properly
                                                              tied together
                                                              Heterogeneous clay liner
                                                              material
                               •  Improper  sealing  around
                                  penetrating  objects

                               •  Sediment  entering into
                                  systems

                               •  Inadequate management
                                  of  personnel
                            Areas of high permeability     •  Substandard compaction
 •  Do  not construct  during winter  in
   cold climates.
 •  Cover liner with  soil blanket or other
   Insulation material when cold weather is
   anticipated.

 *  Increase compact!'ve effort.
 •  Cease construction till spring.

 •  Place rip-rap on  lagoon sidewalls
   extending from below liquid level into
   the freeboard area.

 •  Scarify or disk lower lift prior to
   installing next lift.
 •  Ensure moisture content of last lift
   and lift being installed are the same.

 •  Closely inspect liner material  at
   borrow site or as it is being
   installed and reject coarse-grained
   material.

0  Avoid liner penetrations  in design.
•  Seal properly around penetrating objects.

•  Cover system with geotextile or
   graded  soil  layer.
   Initiate personnel  training  program.
   Cover system with geotextile or  soil
   cover prior to waste  management.
   Design system to minimize  protrusions
   (manholes,  etc.)  in waste  emplacement
   areas.
                                                            •  Conduct proper CQA and CQC, including:
                                                               --  Monitoring for'material variability
                                                               --  Observation of compaction operations
                                                               —  Moisture/density/permeability tests.

-------
 5.5  REFERENCES

 AASHTO:  The Anarjcan Association of State  Highway and Transportation
      Officials.  1978.  Standard Specifications  for Transportation Materials
      and Methods of Sampling and Testing, Part 2, Methods of Sampling and
      Testing, 12th edition.   Washington, D.C.

 Anderson, D.  1982.  Inplace Closure of Hazardous Waste Surface
      Impoundments (draft), Chapter 5—Evaluating Stabilized Waste Residuals.
      EPA-68-83-2943.

 API.   1982.   American Petroleum Institute.  API Recommended Practice:
      Standard Procedure for  Testing Drilling Fluids.  API RP13B.  American
      Petroleum Institute, Dallas,  Texas.

 ASTM.  1985.  The American Society for Testing and Materials.  1985 Annual
      Book of ASTM Standards,  Volume 4.08, Soil and Rock; Building Stones.
      Philadelphia, Pennsylvania.

 Bass, J.   1986.  Avoiding Failure  of Leachate Collection and Cap Drainage
      Systems, EPA 600/2-86-058,  U.S.  Environmental Protection Agency,
      Cincinnati,  Ohio  55268.

 Bernreuter,  D. L., and D. H.  Chung.  1984.  Earthquake Hazard Analysis for
      Nuclear Power Plants, Energy  and Technology Review.  Lawrence Livermore
      National Laboratory, Livermore,  California.

 Bishop, A. W.  1955.  The Use  of the Slip Circle in the Stability Analysis
      of Slopes.  Geotechnique.   5(1):1-17.

 Bishop, A. W., and N. R. Morgenstern. 1960.  Stability, Coefficients for
      Earth Slopes.  Geotechnique.   10(4):129-150.

 Boutwell, G. P.,  Jr., R. B. Adams,  and D. A. Brown.  1980.  Hazardous Waste
      Disposal  in  Louisiana.  Geotechnical Aspects of Waste Disposal.
      American Society of Chemical  Engineers, A Two-Day Seminar.

 Boutwell, G. P.,  Jr., and V. R.  Donald.  1982.  Compacted Clay Liners for
      Industrial Waste Disposal.  American Society of Slvll Engineers,
      National  Meeting,  Las Vegas,  Nevada.

 Cashman,  P.  M., and E.  T. Haws.  1970.  Control of Groundwater by Water
      Lowering. Chapter 3 in:  Ground Engineering, Institution of Civil
      Engineers, London.

 C1chow1cz, N.  L.,  R.  W. Pease, Jr., P. J. Stoller, and H. J. Yaffe.
      1981.   Use of Remote Sensing Techniques 1n a Systematic Investigation of
     an Uncontrolled  Hazardous Waste  Site.  EPA 600/2-81-187,  U.S.
     Environmental  Protection Agency, Cincinnati, Ohio.

Daniel, D. E.  1981.  Problems 1n Predicting the Permeability  of Compacted
     Clay Liners.  Symposium on Uranium Mill Tailings  Management, Fort
     Collins, Colorado,  pp.  665-675.

Daniel, D. E.  1984.  Predicting Hydraulic Conductivity of Clay Liners.
     Journal  of Geotechnical  Engineering.   110(2):285-300.

                                    5-112

-------
 Daniel, D. E.  1987.  Hydraulic. Conductivity; Tests  for  Clay  Liners.  Ninth
      Annual Symposium on Geotechnical  and Gebhydrological Aspects of Waste
      Management-— Colorado State University,  Fort Collins, Colorado.

 Daniel, D. E., and R. E. Olson.   1980.  Geotechnical Aspects  in Design
      of Disposal  Sites for Low-Level  Radioactive Wastes.  American Society of
      Civil Engineers, Texas Section  Meeting,  San Antonio, Texas.

 D'Appolonia,  D. J.  1980.  Soil-Bentonite Slurry Trench Cutoffs.
      Journal  of the Geotechnical  Engineering  Division, ASCE.  GT-4:389-417.

 Davis,  F.  J.   1966.  Summary of  Bureau of Reclamation Experience in
      Statistical  Control  of Earth Dam  Embankment Construction.  National
      Conference on Statistical Quality Control Methodology in Highway and
      Airfield Construction,  University of Virginia, Charlottesville.

 Day,  M. E. 1970.   Brine  Pond Disposal  Manual.  Office of Solid Waste
      Contract No.  14-001-1306, U.S. Bureau of Reclamation, Denver, Colorado.

 Day,  S. R., and D.  E.  Daniel. 1985.   Hydraulic Conductivity of Two
      Prototype Clay Liners.   In:   Land  Disposal of Hazardous Waste:  Proceed-
      ings  of  the Eleventh  Annual  Research Symposium.  EPA/600/9-85/013.
      U.S.  Environmental Protection Agency, Cincinnati, Ohio.

 Diamond, S.   1979.   Preliminary Report  on Analysis and Testing Concerning
      Polymer  Bentonite Lagoon Seal at Wurtsmith Air Force Base,  Oscoda,
      Michigan.  Prepared for  Slurry Systems, Inc., Gary, Indiana.

 Dobrin, M. B.   1960.   Introduction to Geophysical  Prospectinq.
      McGraw-Hill, New York.

 Eagling, D. G.  1983.  Seismic Safety Guide.  LBL-9143,  Engineering and
      Technical Services Division, Lawrence Berkeley Laboratory,  University of
      California, Berkeley, California.

 EERC:   Earthquake Engineering Research Center.  1984.   Computer  Software
      for Earthquake Engineering.  National Information Service for Earthquake
      Engineering, University of California, Berkeley,  California.

 Elsbury, B. R., J. M. Norstrom,  D. C. Anderson,  J.  A.  Rehage, J. 0.  Sai,
     R. L. Shiver and D. E. Daniel.  1985.  Optimizing Construction  Criteria
      for a Hazardous Waste Soil  Liner Phase I  Interim  Report.  EPA-68-08-
     3250, U.S. Environmental Protection Agency,  Cincinnati,  Ohio.

 Ely, R. L., Jr., G. L. Kingsbury, M.  R. Branscome,  L.  J. Goldman,  C.  M.
     Northelm, J. H. Turner, and F. 0. M1xon,  Jr.   1983.  Performance of Clay
     Caps and Liners for Disposal Facilities.   Final Report.   EPA  Contract
     No. 68-03-3149.  U.S. Environmental Protection  Agency,  Cincinnati,  Ohio.

Esu, F.  1966.  Short-Term Stability  of Slopes 1n  Unweathered Jointed
     Clays.  Geotechnique.  16(4):321-328.

Fang, H.-Y. 1975.  Stability of  Earth Slopes.  Chapter 10  1n:  Wlnterkorn,
     H. F., and H.-Y. Fang, Foundation Engineering Handbook,  Van Nostrand
     Reinhold, New York.


                                   5-113

-------
 Fellenius, W.  1927.  Erdstatische Berechnungen  (Calculation of the
      Stability of Slopes).  W. Ernst und  $ohn, Berlin.

 Fenn, D. G., et al.  1977.  Procedures  Manual for Ground-water Monitoring
      at Solid Waste Disposal  Facilities.   EPA-530/SW-G11, U.S. Environmental
      Protection Agency, Office of Solid Waste, Washington, D.C.

 Freeze, R. A., and J. A. Cherry.   1979.  Groundwater.  Prentice-Hall,
      Inc., Englewood Cliffs,  New  Jersey.

 Geo-Con, Inc.  1984.  Soil Bentonite Liners.  Pittsburgh, Pennsylvania.

 Ghasseml,  M., M. Haro, and L. Fargo. 1984.  Assessment of Hazardous Waste
      Surface Impoundment Technology (Case Studies and Perspectives of
      Experts) (draft).  EPA-68-02-3174, U.S. Environmental Protection Agency,
      Multidisciplinary Energy and Environmental  Systems and Applications,
      Torrance, California.

 Ghasseml,  M., M. Haro, J. Metzgar,  M. Powers, S. Qulnlivan, L. Sdnto,
      and H.  White.  1983.  Assessment of  Technology for Constructing Cover
      and Bottom Liner Systems for Hazardous Waste Facilities (Final Report)
      EPA 68-02-3174, U.S. Environmental Protection Agency, Cincinnati, Ohio.

 Gordon,  M. E., P.  M. Huebner,  and P. Kmet.  1984.  An Evaluation of the
      Performance of Four Clay-Lined Landfills in Wisconsin.  Seventh Annual
      Madison Waste Conference,  University of Wisconsin, Madison, Wisconsin.

 Hays, W. W.   1980.   Procedures  for  Estimating Earthquake Ground Motions.
      USGS  Prof.  Paper 1114.   U.S. Government Printing Office, Washington,
      u.C.

 Haxo, H. E.   1980.   Interaction of  Selected Lining Materials with Various
      Hazardous Wastes—II.  In:   Disposal  of Hazardous Wastes—Proceedings of
      the Sixth Annual  Research Symposium,  pp. 160-180.

 Haxo, H. E.,  et al.   1983.  Lining  of Waste Impoundment and Disposal
      Facilities.  SW-870,  U.S. Environmental  Protection Agency,  Cincinnati,
     Ohio.
                                                     «

 H1lf, J. W.   1975.   Compacted Fill.  Chapter 7 1n:   Wlnterkorn,  H.  F.,  and
     H.-Y. Fang, Foundation Engineering  Handbook, Van Nostrand  Relnhold.  New
     York.

 IMC.  1982.  The Role of Bentonite  1n Soil Sealing Applications  (Promotional
     Literature).  Mundeleln., Illinois.

Johnson Division.  1975.  Groundwater and  Wells.   UOP, Inc.,  St.  Paul,
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Johnson, A. W., and J. R. Sallberg.  1960.  Factors that Influence  Field
     Compaction of Soils.  Bulletin 272.  Highway Research Board, Washington,
     D.C.
                                    5-114

-------
 Johnson, H. V., S. J. Spigolon, and R. J.  Lutton.   1983.   Geotechnlcal
      Quality .Control:  Low-Level Radioactive Waste  and  Uranium Mill Tailings
      D1sposaUajC-1l1t1es.  NUREG/CR-3356,  U.S.  Nuclear  Regulatory Commission,
      Washington, D.C.

 Johnson, J. J., and F. J. Gelsel.  1979.   Clay  Caps Lagoon System.  Water
      and Sewage Works.  126(11):30-31.

 Johnson, P. E., and S. W. Cole.  1976. Benton1te/Glac1al Till:  The
      Right Mixture for Lining Brown Co. Cascade Mill Lagoons.  Paper Trade
      Journal.  160(16):36-38.

 Jorgenson, J. L.  1971.  Development and Trial  Use  of Acceptance Sampling
      Plans for Compacted Embankments.  Highway  Research Record.  357:24-34.

 Kmet, P.,  K. J. Qulnn, and C. Slavlk.  1981. Analysis  of Design Parameters
      Affecting the Collection Efficiency of  Clay Lined  Landfills.  Fourth
      Annual Madison Conference of Applied  Research  and  Practice on Municipal
      and Industrial Waste, University of Wisconsin,  Madison, Wisconsin.

 Kotzlas, P. C., and A. C. Stamatopoulos.   1975. Statistical Quality
      Control at Kastrakl Earth Dam.  Journal  of the Geotechnlcal Engineering
      Division, ASCE.  101(GT9):837-853.

 Kozickl, P., and D. M. Heenan.  1983.  Use of Bentonlte as a Soil Sealant
      for Construction of Undersea!  Sewage  Lagoon Extension, Glenboro
      Manitoba.  Short Course  on Waste Stabilization  Ponds, Winnipeg,
      Manitoba.

 Lambe,  T.  W., and R. V. Whitman.  1969.  Soil Mechanics.  John WHey and
      Sons, New York.  pp. 353-373.

 LARG.  1982.  Seismic Location Standard.   LARG-830131.  Llvermore
      Associated Research Group,  Inc.,  Llvermore, California.

 Lundgren,  T. A.   1981.   Some  Bentonlte Sealants 1n Soil Mixed Blankets.
      In:   Proceedings, of the  Tenth  International Conference on Soil Mechanics
      and Foundation Engineering,  Stockholm.

 Lutton,  R.  J.,  G.  L.  Regan, and  L.  W.  Jones.  1979.  Design and
      Construction  of Covers for  Solid  Waste Landfills.  EPA-600/2-79-165,
      U.S.  Environmental  Protection  Agency, Cincinnati, Ohio.

 Lutton,  R.  J., w.  E.  Strohm, Jr., and A. B. Strong.  1983.  Subsurface
      Monitoring Programs at Sites for Disposal of Low-Level Radioactive
      Waste.   NUREG/CR-3164, NTIS, Springfield, Virginia.

Makd1s1, F.  I., and H. B. Seed.  1978.  Simplified Procedures for Estimating
      Dam and  Embankment.  Earthquake Induced Deformations.  Journal  of the
     Geotechnlcal Division, ASCE.   109 (GT7).

Miller-Warden Associates.  1965.  Development of Guidelines for Practical
     and Realistic Construction Specifications.   NCRHP Report 17.   Highway
     Research Board, Washington, D.C.
                                    5-115

-------
 Mitchell, J. K.  1976.  Fundamentals of Soil Behavior.  John Wiley and
      Sons, Inc., New York.

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      of Compacted Clay.  Journal of the Soil Mechanics and Foundations
      Division, ASCE., 91(SM4):41-65.

 Morrison, W. R., E. W. Gray, Jr., D. B. Paul, and R.  K.  Frabel.  1982.
      Installation of Flexible Membrane Lining 1n  Mt.  Elbert  Forebay
      Reservoir.  REC-ERC-82-2.  U.S. Bureau of Reclamation,  Denver, Colorado,

 Olson,  R. E., and D. E. Daniel.  1981.  Measurement of the Hydraulic
      Conductivity of Finegrained Soils.  ASTM STP 746.  pp.  18-64.

 Pelrce, J. J.,  G. Sallfors,  and E. Peterson.  1986.   Clay Liner  Construction
      and Quality Control.  ASCE Journal  of Environmental Engineering,
      February 1986.  112(1):13-24."

 Perloff, W.  H.   1975.   Pressure Distribution and  Settlement.  Chapter 4
      1n:  Winterkorn,  H. F.  and H.-Y.  Fang,  Foundation Engineering Handbook,
      Van Nostrand Reinhold,  New York.

 Rogowskl,  A.  S., and E. B. Richie.  1984.   Relationship  of Laboratory
      and Field  Determined Hydraulic Conductivity  in Compacted Clay Soils.
      In:  Proceedings  of Sixteenth Mid-Atlantic Industrial Waste Conference,
      Pennsylvania State University, University Park.

 Rollins, M.  B.   1969.   Sealing Properties  of Bentonite Suspensions.  Clays
      and Clay Minerals. 16:415-423.

 Ryan, C. R.   1984.   Barriers-Technology  and  Construction.  Seminar
      Presented  at the  Hazardous Materials  Control  Research Institute
      Conference, Washington, D.C., November  7.

 Schmednecht,  F.  C.,  and J. Harmston.  1980.   Vibrated  Beam Techniques for
      Cutoff Wall  Construction.  Presented  at ASCE  and  AEG Meeting, North
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 Schuster,  R.  L.,  and R. J. KMzek.   1978.  Landslides:  Analysis and
      Control.  TRB  Special Report  176, National Academy of Sciences,
     Washington,  D.C.

 Seed, H. B.   1975.   Earthquake Effects on Soil-Foundation Systems.
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     Engineering Handbook, Van  Nostrand Reinhold, New York.

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     Considerations.  Transportation Research Record  897:1-8, National
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     of the Soil Mechanics  and Foundations Division, ASCE.  93(SM4):377-401.
                                    5-116

-------
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       in Dispersive Clays.  In:  Dispersive Clays, Related Piping,  and Erosion
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       1963.  Earth and Earth-Rock Dams.  John Wiley and Sons, New York.

 Small, D. M.  1981.  Establishing Installation Parameters for Installing
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      Parallel  Intersllce Forces.  Geotechnlque 17:11-26.

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      Ohio.

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      New York.  pp.  406-479.

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      U.S. Department of the Interior,  Washington, D.C.

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      Washington, D.C.

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      1110-2-1906, Washington, D.C.

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      Construction Quality Assurance for Hazardous Waste Land Disposal
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      October 1986.  Washington, D.C.

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                                    5-118

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     Losses—A Guide to Conservation Planning.   USDA Agriculture Handbook
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Wong. J.  1977.  The Design of a System for Collecting  Leachate  From a
     Lined Landfill Site.  Water Resources  Research.  13(2).

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                                   5-119

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                                   CHAPTER  7

                            CLAY LINER  PERFORMANCE
 7.1  INTRODUCTION
      Knowledge of the  performance  of  existing  liner designs under field con-
 ditions  is  an  important  factor  for evaluating  the adequacy and practicality
 of various  designs for compacted clay liners.  As part of this project, an
 attempt  was made  to gather  clay liner field performance information.  At the
 onset of this  effort,  only  clay-lined hazardous waste sites with lysimeters
 or leak  detection systems were  deemed suitable for our purposes.  As work
 progressed, however, it  became  apparent that additional sites without
 lysimeters  or  leak detection  systems  that contained predominantly nonhazard-
 ous wastes  might  also  be useful.   In  addition, several facilities that are
 unlined  but located in deposits of low-permeability soil were included in the
 case  study  section. The inclusion of such sites is generally for the
 illustration of a specific  performance problem.

      The success  or failure of  a disposal site depends upon many factors,
 most  of  which  are unrelated to  the type of waste contained within.  Hazardous
 and nonhazardous  waste sites  are probably equally susceptible to the physical
 failure  mechanisms discussed  in previous chapters.  This is not the case,
 however,  where chemical  and clay interactions are important; in these cases,
 industrial  and chemical  waste disposal sites have a greater probability of
 displaying  these  effects than do municipal or nonchemical waste sites.
 Therefore,  by  including  as  many different types of sites (municipal, indus-
 trial, and  chemical) as  possible,  problems resulting from most types of
 failure  mechanisms can be "tested  for" through the analysis of the site data.

      This chapter discusses the various factors affecting clay liner perform-
 ance  as  well as the techniques  and problems of clay Jiner performance moni-
 toring.   Section  7.2 of  this  chapter  is a detailed discussion of 17 facility
 case  studies.   This section includes  such information as the age of the
 facility, liner specifications, construction techniques, waste types, local
 hydrology and  geology, and  facility performance.  Section 7.3 contains a sum-
 mary  of  the information  presented  in  the case study discussions.  The
 relationship between the number of successes and failures of the three facil-
 ity types (lined with  compacted soil,  lined with admixed materials,  or
 unlined)  is also  presented.   Sections 7.4 to 7.7 include discussions on
 various  factors that influence  a facility's performance and methods  for moni-
 toring that performance.  The final section, Section 7.8, presents the
 conclusions that  can be drawn from the chapter.

 7.2  CASE STUDIES

     This section contains descriptions of 17  clay-lined facilities  listed  in
Table 7-1.  The data for these facilities  were obtained  from State and Fed-
eral agencies,  commercial waste disposers,  clay liner  design and construction


                                     7-1

-------
firms, and the industrial sector.  Information on approximately 50 other dis-
posal facilit4es was also obtained during this effort and previous data-
gathering efforts.  In most cases, either necessary information was not
available or the facility did not have any unique features worthy of dis-
cussion.  Several medium-scale field studies also provide an insight into
the performance of field-compacted clay liners (Day and Daniel, 1985; Bagchi,
1987; Rogowski et al., 1985; Rogowski, 1986).

7.2.1  Criteria for Site Selection

     Several important sets of data are needed in order to evaluate the
effectiveness of a disposal site.  These include:

     •  Geologic and hydrogeologic site characteristics

     •  Types of waste in the site

     •  Geotechnical characterization of the clay

     e  Leachate collection, leak detection, or groundwater monitoring
        data

     •  Physical description of the site

     a  Liner description

     •  Construction procedures.

Many times, while the files on specific sites were reviewed, it became
obvious that critical  sets of data were either fragmentary or not available.
One reason for this is that many sites had been "grandfathered in" when the
States started permitting disposal facilities.  In this circumstance, impor-
tant information, which is now required before a site can receive a permit,
was never developed or submitted to the States when these older sites were
started.  For this reason, even though we know about the existence of many
old clay-lined sites,  their Incomplete documentation makes them unsuitable
for our purposes.

     In some cases, when sites have been suspected of* causing groundwater
pollution, the State or landfill operator has initiated a hydrogeological
study designed to evaluate the performance of the clay or soil leachate
barrier.  Sites where these studies have been performed are among the best
documented and are included in our data base.  However, the motivation for
performing these studies was the suspicion of poor performance, and their
Inclusion here may distort our perception of the capabilities of clay liners
in general.  We have no way of including the hundreds of undocumented clay-
lined sites that may be performing well.

     As one might suspect, the best documented sites are those relatively few
that have been built after the institution of strict permitting requirements
at the State and Federal level.  In general, permit files contain hydrogeo-
logical  reports and engineering reports that document the installation of the
facility and the characteristics of the clays used.  Typically, however,
these sites are only a few years old and therefore do not supply much data
relevant to the prediction of the long-term performance of clay liners.


                                     7-2

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                                                                   TABLE  7-1.   CLAY-LINED  FACILITY  INFORMATION
                        Site      Startup  date
Waste type
      Liner description
(liner components listed from
        the top down)
Facility performance and comments.
CO
                                     1976           NHa  and  HUb
                                     1971           NH  and  HW
                                                   (including  un-
                                                   solidified  liquids)
                                     1977   .        HW  (including
                                                   organic  solvents,
                                                   heavy metal  sludges
                                                   and  acids) high-
                                                   density  polyethylene

                                     1979           HW
                                    Late  1970's   HW
                                     1976
                                                  HW
                                    1955          HW
                               Leachate collec-
                               tion system
                               added  in 1982.
                                    1980
                                    1980
                                    1979
75% MSWC
25% paper mill
sludge

Liquid HW
HW (liquids and
solids)
                                                                           -Unrecompacted  in  situ  glacial  till.
                        -Zone-of-saturation landfill.
                        -In situ glacial till.  Sand or
                         gravel seams were excavated and
                         then backfilled with clay.
                        -Leachate collection system.

                        -In situ clay-shale soil contain-
                         ing calcium carbonate nodules
                         and seams.  Sand or gravel
                         seams were excavated and then
                         backfilled with soil.

                        -Leachate collection system.
                        -80-mil (HOPE) liner.
                        -5-foot recompacted clay liner.

                        -French drain above liner in
                         each cell.
                        -Recompacted Demopolis Chalk.

                        -Leachate collection system
                        -Flexible membrane liner (FML)
                         (Hypalone® or HOPE).
                        -10-foot recompacted clay
                         liner from borrow site.

                        -Leachate collection system.
                        -Unrecompacted glacial till.
-Leachate collection system.
-4-foot recompacted clay liner.
-Three lysimeters.

-5-foot recompacted clay liner.
-Leak detection system.
-5-foot recompacted clay liner.
                                                                          -5-foot recompacted clay liner.
                                                                          -Leak detection system.
                                                                          -1-foot recompacted clay liner.
                                        Original monitoring well installation
                                        problem has been corrected.  No
                                        recent performance problems have been
                                        reported.

                                        Bathtub effect has caused inward
                                        hydraulic gradient to reverse.
                                        Severe groundwater contamination
                                        has resulted.
                                        Groundwater contamination has
                                        occurred, possibly due to a
                                        reaction between the low pH waste
                                        and the calcium carbonate inclusions
                                        in the local soil.

                                        No performance problems.
Minor problems, including buildup
of leachate head, have been
corrected.

Leachate removed from collection
system is less contaminated than
the groundwater.  Contamination
was caused by an adjacent facility
requiring remedial action.

Contamination in well is thought
to have come from an adjacent
abandoned drum storage facility by
way of a sand and gravel seam.

Initial collection of liquid in
lysimeters thought to be soil mois-
ture release following construction.

Desiccation cracks formed in
unprotected liner prior to filling
with waste.  When pond was filled,
waste migrated into the detection
system.

Chlorinated organic liquid placed
in pond caused liner failure.
                                                                                                                                         (continued)

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                                                                TABLE 7-1  (continued)
Site     Startup date
Waste type
              1981
Liquid
             1978
                           HW
             1977
             1974
             1980
             1980
                           HU
                           MSW
                           HU
                           HW
             1976
      Liner description
(liner components listed fro*
         the top down)
                                                   -3-foot recompacted clay  liner.
                                                   -Leak detection system.
                                                   -1-foot recompacted clay  liner.
                        -Leachate collection system.
                        -Approximately 2-foot
                         recompacted clay liner.
                        -Leak detection system.
                        -1-foot recompacted clay liner.
                        -Approximately 1-foot compacted
                         soil liner.
                        -Geotextlle.

                        -Leachate collection system.
                        -1-foot recompacted borrow clay
                         soil liner.
                        -Leak detection system.

                        -Leachate collection system.
                        -4-inch bentonlte (averaging
                         11 percent by weight) and
                         sand liner.
                        -Two lysimeters.

                        -Leachate collection system.
                        -4-foot-thlck recompacted local
                         clay Hner with  3 percent benton-
                         ite and 3 percent lime added.

                        -Leachate collection system.
                        -5-foot recompacted soil liner
                         Including a 1-foot layer of
                         bentonlte (9 to  12 percent) and
                         soil.
                        -Leak detection system.
                        -6-inch bentonite and soil  layer.
                        -5-foot in situ soil  layer.

                        -Leachate collection system.
                        -4-inch bentonite/soil  liner.
                        -Leak detection system.
                        -4-inch bentonite/soil  liner.
Facility performance and cownents
                                        Liquid volu«es collected in detection
                                        system were used to calculate liner
                                        permeability.   Values ranged from
                                        4 x 10-8 to 3  x 10? cnt/s.   Recent
                                        major earthquake 100 miles north of
                                        the facility caused no damage.

                                        Failure in upper liner has occurred.
                                        Lower Hner 1s still  functioning.
                                                                                           No performance problems.
                                                                                           Groundwater contamination has been
                                                                                           detected at several monitoring points.
                                                                                           Cap failure caused increased leachate
                                                                                           volumes.  Problem was corrected by
                                                                                           replacing section of cap.
                                                                                           Small amounts of liquid have been
                                                                                           collected in the leak detection
                                                                                           system.  Monitoring wells have
                                                                                           shown no significant changes.
                                                                                           Liquid volumes collected in detection
                                                                                           system were used to calculate the
                                                                                           liner permeability.  Values ranged
                                                                                           from 3 x 10~8 to 6.5 x 10'8 cm/s.
aNH = Nonhazardous.
bHW = Hazardous waste.
CMSH = Municipal solid waste.

-------
      The site data presented  in  the  following  sections  include all of the
 relevant information that was  made available to the authors for each site.
 As discussed in the previous paragraphs,  the quality, quantity, and type of
 these data were quite varied.

 7.2.2  Site A

 7.2.2.1  Physical  Description—
      This sanitary and hazardous waste landfill is located in an area of
 glacial  till  soils.   The  liner at this facility consists of the unrecompacted
 glacial  till,  which  has a relatively low  permeability.  A plan view of the
 facility is presented in  Figure 7-1.

 7.2.2.2  Startup Date—
      This facility began  operations in 1976.

 7.2.2.3  Local  Geology and Hydrology—
      This facility is located  in the midwestern United States.  Average
 annual  precipitation  at this site is 35 inches.

      The soil  in the  vicinity  of the landfill is described as a clay-loam
 till.   Soil  borings  indicate that it extends to depths of 150 feet.  Underly-
 ing the  till  is a  thick formation consisting of limestone, dolomite,  sand-
 stone,  and  slate.  Occasional  gravel, silt, or sand lenses are present in the
 upper till  layers.   It is not  known if these areas were excavated and back-
 filled with  clay prior to waste placement.

      There  is  very little information about the groundwater levels in this
 area.   However, it  is  known that the groundwater flows in a northeasterly
 direction and  that the facility is located in an area where the possibility
 of groundwater  contamination is low.

     Monitoring wells are located both upgradient and downgradient of the
 site.  Samples are analyzed quarterly for abnormalities in groundwater
 conditions.

 7.2.2A  Waste Type--
     Both sanitary and hazardous wastes (including drummed combustibles  and
 Teachable metals) are accepted at this facility.

7.2.2.5  Liner Description—
     The liner at this facility consists  of unrecompacted  in-situ  glacial
till.   This material has the following  characteristics.

     »  Permeability                       3.0  x  10-6  to 5 x  10-8  cm/s
                                           (triaxial  tests with
                                           leachate and  water)

    o  Liquid limit                       22 - 26%

    o  Plasticity  index                    2 - 10%

    »  Moisture content                    12 - 22%

    «  Amount  passing No. 200  sieve        75 - 95%.


                                    7-5

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                                                           Hydraulic Gradient
Monitoring /
  Wells    \
                        Hazardous
                          Waste
                                 .   1,000 feet
                                 ' (approximate)
                            Figure 7-1. Plan view of site A.

                                       7-6

-------
      Compatibility testing performed by a private firm has indicated that the
 leachate win not react with the surrounding liner soils in a way that  would
 significantly increase its hydraulic conductivity.  The major organic
 components of the test leachate were phenol, methylene chloride,  1,1,1-
 trichloroethane, toluene, 1,1-dichloroethane, and diethylphthalate.

 7.2.2.6  Liner System Installation—
      This is an unlined facility.  Methods used for the excavation were not,
 available.

 7.2.2.7  Performance--
      Analysis of groundwater samples taken from the present monitoring  wells
 has not revealed any leachate migration problems.   However, the original
 monitoring wells were improperly installed,  having contained  steel mill  slag
 where clean gravel  should have been used.   Samples taken from these wells  in
 1976 had pH levels  between 10.7 and 11.3.   The analysis also  revealed a
 chemical oxygen demand (COD)  of 3,193 ppm  and a chloride level of 1,028 ppm.
 These elevated levels were attributed to the steel-mill  slag  in the well
 casings.  Samples taken from newly constructed wells  in 1981  had  pH  levels of
 around 7, COD levels ranging from less than  10 ppm to approximately  60  ppm,
 and chloride levels ranging between 4 ppm  and 12 ppm.

 7.2.3  Site B

 7.2.3.1  Physical Description—
      This 166-acre  facility contains an 80-acre zone-of-saturation, or  inter-
 gradient, landfill.  A small  section of the  landfill  has a  recompacted  clay
 liner;  the remainder of the landfill  is unlined.   A leachate  collection
 system (LCS)  lies between the waste and the  landfill  bottom.   A  plan view of
 the facility is presented in  Figure 7-2.

 7.2.3.2  Startup Date—
      This landfill  began  accepting  waste in  1971.

 7.2.3.3  Local  Geology and Hydrology—
      This facility  is  located in  the  northern  central  portion of  the United
 States.   Average annual precipitation at this  facility  is approximately
 30  inches.
                                                    «
      The site  is located  in a glacial till, which  consists primarily of clay
 and  silt.   Site  investigations  have shown that  sand and gravel lenses are  '
 present  throughout  the  till.   Underlying the glacial  till is a layer of
 moderately  fractured dolomite up  to 200 feet thick.  A permeable aquifer
 exists  in this bedrock  layer.  The glacial  till is saturated to within
 10 feet  of  the ground surface.  Groundwater flow was  in a southeasterly
 direction prior  to the development of the disposal facility.

 7.2.3.4  Waste Type—•
     This facility contains municipal solid waste, nonhazardous industrial
waste, and hazardous waste.   Included in this are large amounts of plating
 sludge and pickle liquor as well as smaller amounts of various solvents.
Liquid wastes were not solidified prior to  their disposal.
                                     7-7

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                                           Monitoring Wells
VJ

00
                    Leachate
                    Seeps
                                                                               Old Section
                                                                                No Data
                                                        Figure 7-2. Plan view of site B.

-------
  7.2.3.5   Liner  Description—
  «....  The.u 11nfr  at  this  facility  is a minimum of 30 feet of in situ glacial
  till.  The  glacial  till  has the  following characteristics:         9'acnai

         Soil Characteristics                 Average Value

       •  Amount  passing  No. 200 sieve              68%

       •  Clay                                      4Q%

       •  Liquid  limit                           '   29%

       •  Plastic index   .                         14%

      •  Field permeability                   7.5 x 10-6 cm/s

      t  Laboratory permeability                9 x lO"8 cm/s.

 Lenses of sand or gravel that were encountered during site construction were
 excavated and backfilled with a minimum of 5 feet of recompacted clay.   A
 leachate collection system is located on top of the landfill  base.  Specifi-
 cations for this system were not available.

 7.2.3.6  Liner System Installation--
      No information on the excavation and construction  of  this  facility was
 aval labl e.

 7.2.3.7  Performance—
      Recently,  three major and numerous minor  leachate  leaks  have  been
 observed  in  the  western  side  of the  final  cover (see  Figure 7-2)   The  statP
 ?,eni??!?tS Sttr1bute these 1eaks  to  the 26-foot hydraulic  head w thin the
 landfill   One geologist estimated that,  at  times,  the  head is as  great Is 40
 feet.   This  high hydraulic head has  caused the  inward gradient of  this  zone-
 of-saturation  landfill to reverse.

 in*-« JhfeC°nd Prob.1em.enco"ntered at  this site  is the migration  of leachate
 into the groundwater in  a very small area on the northern  edge of  the land-
 fill (see  Figure 7-2).   Excavations  in  the problem area revealed that in one
 5h2  ilP?T*Ie dep2Slt £hat  had been  1mPr°Perly sealed with clay was belSw
 2!  JXeV! ?he Waste4mater1al •   Leachate entered this permeable  layer and
 was  detected n  a monitoring well.  Remedial action consisting of the instal-
 lation of a  clay cutoff wall and  leachate removal has resulted in some
                   groundWater 9ual1ty; however, significant contamination is
7.2.4  Site C
7.2.4.1  Physical Description—
«« H The JaS1l1ty consists of. 31 small drum disposal  trenches,  4 treatment
ponds, and 2 evaporation ponds (see Figure 7-3).  The total  storage and
disposal area is approximately 16.5 acres.

     The ponds and trenches were excavated in the local  natural  soil    If
sand seams or other potentially troublesome areas were located  in the pond
                                     7-9

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                              a
                                                          a
                                                                                   a
-s]
l-»
o
                   Evaporation
                      Ponds
  D
  D
Treatment
  Ponds
                                                                                       Disposal
                                                                                       Trenches
                                                                                                                                   N
                                     a
                                   •$• Monitoring wells in the upper
                                       water-bearing zone
                                   O  Monitoring wells in the lower
                                       water-bearing zone

                                        Approximate Scale
                                     I           I     	1
                                    0        200 ft       400 ft
                                                                Figure 7-3. Plan view of site C.

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 bottoms, these areas were recompacted.  No recompacting was done 1n  the
 disposal trenches.  Several  monitoring wells surround the facility.

 7.2.4.2  Startup Date—
      The facility was opened in 1977, but because of groundwater contamina-
 tion it was forced to close  in January 1982.  Since that time,  changes have
 been made and parts of the facility are again in operation.

 7.2.4.3  Local Geology and Hydrology—
      This facility is located in the midwestern  plains  of the United States.
 Average annual precipitation in this area 1s approximately 25 inches.

      Investigations have indicated the presence  of two  water-bearing zones
 beneath the facility at depths of approximately  40 and  50 feet  below the
 ground surface.  Several  springs and a creek are to the north of the facil-
 ity.  The relationship between the groundwater zones  and springs is unknown.

      Soil  borings indicate that approximately 3  feet  of topsoil  overlie 30 to
 40 feet of weathered clay-shale.  This weathered clay-shale is  a plastic
 silty to highly plastic clay (CL to CH) with calcium  carbonate  nodules and
 seams throughout.  Bedrock lies under the clay-shale  layer.  An  example of a
 typical  soil  boring is illustrated in Figure 7-4.

 7.2.4.4  Waste Type-
      Various  hazardous wastes  including organic  solvents,  heavy metal
 sludges,  and  acids  were held in the treatment  and  evaporation ponds and
 disposed of in the  drum storage area.

 7.2.4.5  Liner Description-
      While  this facility  is  almost completely  unlined,  potential problem
 areas uncovered by  the pond  excavations,  such  as sand seams, were
 recompacted.

 The  local  clay-shale  soil  was  the  only barrier to waste migration.  A cross
 section  of  the facility is presented  in Figure 7-4.

 7.2.4.6   Liner System Installation-
      Information  about the procedures  used to  excavate and  recompact the
 disposal areas was  not available.   Methods used to  install the monitoring
 wells were  also not available.

 7.2.4.7  Performance—
      Analysis  of  groundwater samples  indicates that contamination has
 occurred.   Elevated concentrations  of  chromium, arsenic, barium, cadmium,
 lead, and mercury were detected  near the disposal ponds and trenches.
 However, except for chromium, none  of  the heavy metals were detected in
 offslte monitoring wells.  In addition to heavy metal contamination,  several
 volatile organics such as  chloroform,  trichloroethane, dlchloroethane,
 benzene, and methylene  chloride were detected in both onsite and offsite
monitoring wells.  The highest  levels of volatile organics were  found onsite
 in the uppermost water-bearing zone in wells closest to the disposal  areas.
Base-neutral-extractable organics and acid-extractable organics  were  also
detected in onsite and some offsite wells (see Table 7-2).
                                    7-11

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                      Evaporation
                         Pond
Treatment
  Pond
Disposal
 Trench
VI
i-»
to
                                           Upper Water-
                                           Bearing Zone
                                           Lower Water-
                                           Bearing Zone
                                                                                                    40ft
                                                                                                                 Topsoil
                                                                Clay-shale
                                                                soil with
                                                                calcium carbonate
                                                                nodules and
                                                                seams
                                                                Bedrock
                                      Figure 7-4. Cross-sectional view of site C (vertical dimensions are to scale).

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              TABLE 7-2.   GENERAL  OCCURRENCE OF CHEMICAL PARAMETERS IN THE GROUNDWATER AT SITE C
No.
Parameter parameters
tested for tested for
Volatile organics-
No. found 31
Highest
concentration
Trace metals-
No, found 8
Highest
concentration
Acid-extractable
organics
No. found n
Highest
concentration
Base-neutral- t
extractable organics
No. found 46
Highest
concentration
No. parameters
Onsite
detected

Upper water- Lower water-
bearing zone bearing zone

20

370,000 3

8

20,000


6

24,000


11

410

19

,100

8

500


ND

ND


3

83
and highest concentration
Off site
Upper water-
bean" ng zone

18
±\j
79,000

8
\j
300


3

3,300


6

250
(ppb)

Lower wat,er-
bearing zone

£
D
510

7
/
500


MD
IMU
ND


i
J.
160
ND = No parameters of this type were detected.

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     Investigations of the groundwater contamination at this facility suggest
that the treatment ponds are the major source of contamination 1n the upper-
most water-bearing zone.  This conclusion is based on the fact that the
materials 1n the ponds were usually of low pH and would be reactive with the
carbonate seams and inclusions in the surrounding soil.  Several  of the
trenches were used for the disposal of highly acidic waste oil reprocessing
sludges.  These sludges may have also attacked the surrounding materials and
allowed contamination to occur.

7.2.5  Site D

7.2.5.1  Physical Description--
     This recompacted clay- and synthetic-lined hazardous waste disposal
facility consists of two large disposal sections, each of which is divided
into several smaller disposal cells.  These in turn are divided into three
subcells each for the segregation of different waste types.  Four of the five
disposal cells in Section I are closed, and the remaining cell is currently
active.  The first of 10 proposed disposal cells in Section II 1s under
construction.  This construction is scheduled to be completed in the fall  of
1984, at which time landfill ing operations will be initiated.  A plan view of
the facility is presented in Figure 7-5.

7.2.5.2  Startup Date--
     Construction of this facility was started in 1979.

7.2.5.3  Local Geology and Hydro!ogy~
     This facility is located in the southeastern United States.  Average
annual precipitation at this site is approximately 47 inches.

     Information on the local geology and hydrology was obtained through the
use of 32 exploratory borings.  These borings have confirmed that there are
several distinct soil layers.  The lowest of these layers 1s the Tuscaloosa
Formation, which is overlain by the Black Mingo Formation, which in turn is
overlain by Quaternary deposits.  The upper surface of the Tuscaloosa
Formation 1s located approximately 55 to 120 feet below the ground surface-
This material consists of clayey sands and clays.  Lenses or beds of coarse
to fine sand are located in this formation.  In situ hydraulic conductivity
testing of this formation revealed that it has a permeability 1n the
range of 1.09 x 10~6 to 4.01 x 10~6 cm/s.           *

     The Black Mingo Formation encountered at this site consists of four
subunlts:  the Basal Clay Unit, the Opal Claystone Unit, the Red Sand Unit,
and the Buhrstone Unit.

     The Basal Clay Unit consists of very hard black clay with frequent sand
and silt lenses.  The upper surface of this material is located approximately
60 to 115 feet below ground level and varies in thickness from 1.5 to 15.5
feet.  In a few of the borings, this material was not present.

     The Opal Claystone Unit, on the other hand, is either above the
Tuscaloosa or Basal Clay Formations over the entire site.  This material con-
sists of low-permeability (exact value unknown) silt and clay with very few
sand Inclusions.  The thickness of this formation varies from 20 to 60 feet.
                                    7-14

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VI

l-»
U!
                                                                                       Section II
                                     Direction of
                                     Ground and
                                     Surface Water
                                     Flow
                                                                                              Clay stone
                                                                                              Processing
                                                                                              Facility
                                                                    Drum Storage and
                                                                    Waste Handling Facility
                                                                                          Section I
                                                                                                             N
                                                                                                              Scale
                                                                                                                I
                                                                                                              400'
  I
800'
                                                          Figure 7-B. Plan view of site D.

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      The Red Sand Unit,  which  is  located above the Opal Claystone Unit,
 consists of sand to clayey silts.  The  silts and clays are generally present
 as 1/4-inch"lo 2-inch  layers interbedded with the sand.  The thickness of
 this  formation varies  from 0 to 15 feet.   In situ hydraulic conductivity
 testing  of this material  revealed that  its permeability ranges from
 6.24  x  1C-5 to 6.43 x 10'4 cm/s.

      The final  unit of the Black Mingo  Formation, the Buhrstone Unit, is
 found scattered over the entire area.   When present, it ranges up to 14 feet
 thick.  This material  is described as clayey silt to silty clay.

      The Quaternary deposits contain layers of variegated clay that were
 originally thought  to  be a source of low-permeability liner material.
 Further  investigations revealed that the silt and sand content was much too
 high  for it to  be used as a base liner.

      An  aquifer is  present in  both the  Tuscaloosa and the Red Sand Forma-
 tions.  The Tuscaloosa aquifer is approximately 60 to 70 feet below the
 ground surface.  The Red Sand  aquifer is roughly 40 feet above this aquifer.
 The direction of flow  in  both  cases, as well as the direction of surface-
 water flow,  is  toward  a  lake located southwest of the facility.

 7.2.5.4   Waste  Type—
      This facility  accepts most types of hazardous wastes.  These wastes are
 classified as alkaline,  acid,  or organic and are disposed of with similar
 wastes only.  This  is  accomplished through the use of three subcells that are
 incorporated Into all  of the cells in Section II of the facility.  The size
 of each  of the  subcells  was determined  so that maximum separation of
 potentially incompatible wastes was provided and based on past operating
 experience.

 7.2.5.5   Liner  Description—
      The liner  at this facility consists of 5 feet of recompacted clay
 (maximum permeability  of 1 x 10-' cm/s) brought to the facility from a
 borrow pile located several miles away.  Ten-foot sidewall liners are present
 above the top of the Opal  Claystone Unit (see Figure 7-6).  An 80-m1l high
 density  linear  polyethylene (HOPE) membrane liner lies on top of the
 recompacted clay.   This  liner  is protected with a soil layer that is 9 inches
 deep  on  the bottom  and 24 inches deep on the sidewafls.  A leachate collec-
 tion  system 1s  located on top  of the protective soil layer (see Figure 7-6).

      The subcell  separation berms are constructed of recompacted clay and are
 built up in  5.5-foot-high sections as the landfill operations progress.  The
 side  slopes  of  these berms are 1:1.

 7.2.5.6   Liner  System  Installation-
      Prior  to excavation  of the landfill cells, a channel  to drain the
 perched water table  within  the Red Sand Unit was constructed.  After this
 channel was completed  and  in operation, excavation of the landfill cells was
 Initiated.  Side  slopes were cut on a 3:1 (horizontal:verticle) slope down to
 the top of the  Opal  Claystone Unit.  At this location, a 17-foot-wide "bench"
with a 3-foot-wide trench was excavated into the top of the opal  Claystone
 (see Figure 7-6).  This area was excavated to provide  room for a  thicker
 Uner.  Below the "bench,"  side slopes were also 3:1.   A minimum  of 10 feet
of the opal Claystone was  left as foundation material.  At the leachate


                                    7-16

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       10 ft Recompacted
       Clay Liner
                         Side Wall
                      1  Slope
 I
}-»
VI
    In Situ
Opal Claystone
                                24 in Protective
                                Soil Cover
                                        80 mil HOPE
                                        Liner
                                                                                     1-ft Drainage
                                                                                     Layer
Typical 5.5 ft-High
Section of a Cell
or Subcell Separation
Berm
                                                                                                                 .,*-
                                                 9-in Protective
                                                 Soil Cover
                                                                                                  4-in Perforated
                                                                                                  Collection Pipe
                                                                        rr*
                         5 ft Recompacted
                         Clay Liner
                                                                                \\  //   \\   //  \\   //   \v\//
                                                                                                               \
                                                                                                      Filter Fabric
                                                                                                          \\
                          Figure 7-6. Cross-sectional view of site D liner.

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 collection system sump locations,  approximately  4.5  feet  of opal claystone
 remained as the foundation.

      After the sides and base of a cell were  graded,  clay was brought to the
 site from the borrow area.   Before the  clay was  placed  in the excavation, a
 "test fill" was constructed  with borrow soil  that was selected based on the
 basis of laboratory screening procedures.  The "test  fill" was constructed in
 the field with equipment and procedures that  were to  be employed during liner
 construction.  Undisturbed Shelby  tube  samples were  taken from the completed
 "test fill" and were tested  in the laboratory for density, moisture content,
 and permeability.   The clay  was compacted  in  6-  to 8-inch lifts with either a
 sheepsfoot or smooth-drum vibratory roller.   The liner specifications
 required a permeability of 1 x 10~7 cm/s or less.  Testing results from
 the construction quality assurance (CQA) tests on the installed liner were
 not available;  however,  results from tests performed on Shelby tube samples
 taken from the "test fill" were as follows:

      a  Density             114.9  - 120.0  lb/ft3

      •  Water content       22.6 - 29.8%

      •  Permeability        1.8 x  10~8 to 8.0 x  ID'8 cm/s.

 7.2.5.7   Performance--
      Groundwater samples taken from upgradient and downgradient monitoring
 wells have not  been  statistically  different since the start of waste
 placement.

 7.2.6 Site E

 7.2.6.1   Physical Description—
      The  facility presently  occupies approximately 100 acres,  with room for
 expansion  to  340 acres.   There are over 20 disposal  trenches at various
 stages of  operation  as well  as 4 active evaporation ponds (see Figure 7-7).

 7.2.6.2  Startup Date—
      This  facility became active in  the late 1970's.

 7.2.6.3  Local Geology and Hydrology—
     This facility is  located  in the southeastern United States.   Average
annual precipitation at  this facility is^50 inches.

      It is  located in a  natural clay formation called the Demopolis Chalk
Formation.  Testing of the Demopolis Chalk Formation has shown that it  has
the following properties:

     t  Average permeability 4.0 x 10"8 cm/s

     a  Permeability to polychlorinated biphenyl  (PCB)  liquids:

        -  Light oils and PCB's, 9  x lO'9  cm/s
                                   7-18

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                        -4-
Key
   N
        Active Impoundment
        or Trench

        Completed Impoundment
        or Trench


        Monitoring Well


        200 ft (approx.)
                    -4-
                           o
                           o
                           O
                              i  I
                                   Active
                                   Active
                          o
                          Q.
                          O
Proposed
                         Figure 7-7. Plan view of site E.


                                  7-19

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         -   Heavy  oils  and  PCB's,  1.5 x  10-10 cm/s

      •   88% of  the material passes the  No. 200 sieve

      t   35% of  the material is  less than 0.001 mm in diameter

      •   Liquid  limit of 31%

      t   Plastic limit  of 20%.

Soil  borings  in the area have shown that the clay is a minimum of 500 feet
thick and  in  some places extends  to depths of over 700 feet.

      The closest  usable groundwater is  located below this clay formation.
However, a  few  locations of perched water are in the vicinity of the site.
In addition,  the  Demopolis Chalk  Formation is saturated to within 10 to
30 feet of  the  ground  surface.

      The 100-year projected flood elevation for a creek, located 3,000 feet
north of the  facility, is  125 feet above mean sea level.  This should present
no problem  to the facility because the disposal trenches are located at
points that range from 180 to 220 feet above mean sea level.  The lowest
elevation of  the  site  is 148 feet above mean sea level.

7.2.6.4  Waste  Type--
     The site is designed to be a full-service facility that accepts all
types of hazardous wastes.  The majority of the material received for dis-
posal consists  of acidic and caustic Industrial wastes, heavy metal  sludges,
contaminated  containers, sludge, and oil sludges.  All  wastes received by the
facility are  handled separately, and only compatible materials are placed
within proximity of each other.

     PCB wastes are handled separately and only PCB's and PCB-compatible
wastes will be  located in the same disposal trench.

7.2.6.5  Liner  Description--
     Each disposal trench is lined with recompacted native soil.  Construc-
tion  information concerning the number and thlckness.of lifts was not
available.  A calculated amount of absorptive material  is placed on  top of
the recompacted bottom of each trench»  The wastes are then placed on top of
this material and covered with 6 to 8 Inches of the natural clay.  The final
trench covers are also constructed with natural clay.

     The current monitoring system consists of the following:

     •  A subsurface collection system and a secondary retention dam.
        This system would collect any materials that might migrate.

     •  Several  monitoring wells placed within proximity to active
        trenches.

     •  Observation wells surrounding the entire  facility.
                                    7-20

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      A French drain system is located at the lowest  point  in  each  trench.   In
 the event that liquid is collected in this  drain,  it would be pumped out and
 treated as incoming waste.

 7.2.6.6  Liner Installation--
      No information was available.

 7.2.6.7  Performance--
      In general,  this facility is operating as  planned.  There have, however,
 been a few minor  problems.  Groundwater from a  more  permeable weathered sec-
 tion of the Demopolis Chalk Formation has infiltrated  the  sidewalls of
 trenches 15 and 19.  At trench 15, this problem was  remedied  by  installing  a
 cutoff wall on the south-southeast side of  the  trench.  Recompaction of the
 entire sidewall at trench 19 eliminated the groundwater flow  into  this
 trench.  More recently, large volumes of leachate  (up  to 50 feet deep) have
 been accumulating in some of the  trenches with  interim final  covers.  These
 large volumes of  leachate are attributed to the infiltration  of groundwater
 and precipitation.  Frequent pumping  of the leachate has helped to reduce
 these volumes. Final  covers consisting of  3 to 5  feet of  recompacted
 Demopolis Chalk and a HOPE liner  are  scheduled  to  be installed by  the end of
 1986.  In addition, the State monitoring well analysis has shown trace levels
 (92 ppb maximum)  of 12 organic compounds in groundwater samples.  An investi-
 gation of their source indicates  that they  may  have  come from the well casino
 materials.

 7.2.7  Site F

 7.2.7.1  Physical  Description—
      The 380-acre facility consists of  five  secure land disposal  cells with a
 total  area of 25  acres.   Cells  1,  2,  and  3  are  closed; cell 4 is currently
 being  filled;  and cell  5  is  under  construction.  The remainder of the facil-
 ity is  devoted to sanitary landfill ing, waste treatment operations; and
 recovery of lime  from  the  old  slag disposal   operation.

     The  five  cells are  lined with 10 feet of recompacted clay soils.  On top
 of  the  clay liner is a  flexible membrane  liner  (FML), which in turn is
 covered with a 1-foot  layer  of recompacted clay.  A  layer of geotextile lies
 above  the  1-foot  clay  liner.  Finally, a  12-inch drainage blanket containing
 slotted  4-inch  corrugated  HOPE pipe at a minimum of tOO-foot intervals is
 installed  on  top  of the geotextile (see Figure 7-8).

 7.2.7.2  Startup  Date—
     The facility  is located at the site of a slag disposal operation that
 has not been active for 90 years.  The clay-lined facility as  it  currently
 exists  has  been in operation since 1976.

 7.2.7.3  Local Geology and Hydrology--
     This  facility  1s located in the northeastern United  States.   Average
annual precipitation in this area 1s approximately 36 Inches.

     Numerous onsite borings and test pits have revealed  that  the site 1s  an
old disposal area covered with waste industrial  slag  ranging in depth from
approximately 7 feet to 45 or 50 feet.  The  disposed  slag  fill ranged in  size
                                    7-21

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VI
             Flexible
             Membrane
             Liner
                   (Not to scale)
                                                                                                                    Interior
                                                                                                                   Clay Dike
                                                         1-ft Drainage Layer
                                                                         Slotted 4-inch
                                                                         Geotextile Wrapped
                                                                         Leachate Collection Pipes
\\
                                                                                1 to 2 ft Compacted Cover Soil
                                                                                  10-ft Compacted Clay Liner
                                                            \\   //    \\   //    \\   //    \\   //   \\   //   \\   //   \\
                                                      Figure 7-8. Cross-sectional view of site F.

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 from silt-sized particles to boulders.  Beneath the slag was a layer of marsh
 silt that ranged in thickness from a few inches to as much as 5 feet.

      Below the slag and marsh silt materials covering the entire site was  a
 6-foot layer of lacustrine clays.  These clays contained lenses of gray
 nonplastic silts and clay with minor amounts of fine sand.  The presence of
 these lenses throughout the lacustrine clay eliminated it from consideration
 as an in situ liner material.  Laboratory analysis of the lacustrine clav
 indicated that it had the following properties:

      •  Natural  water content             26.5 - 42.8%

      •  Liquid limit    .                  50%

      •  Plastic limit                     22%

      •  Dry unit weight                   99 ib/ft3

      •  Permeability (laboratory          1 x lO"8 to 6  x 10~8 cm/s
         compacted)

      •  Amount passing No. 200            99%
         sieve

      •  Amount passing 2 microns          54 - 63%.

      Underlying  the lacustrine clay was  a 5-foot layer of glacial  till
 consisting of brown to red-brown silts,  clays,  and sands  with  varying  amounts
 of gravel.  Laboratory testing demonstrated that the  permeability  of  the
 till  was 3 x 10-' cm/s,  making it unsuitable for use  as a liner material.

      Groundwater under the facility occurs  in  three zones:

      •   Unconfined  water table above the  lacustrine clays

      t   Confined aquifer in the upper  10  feet  of bedrock

      •   Immobilized groundwater held within  the  impermeable confining
         beds.

      Piezometers installed in  the soil-boring holes indicated that the
groundwater elevations ranged  from 0.5 to 6 feet below the ground surface.

7.2.7A  Waste Type-
     Each of the five disposal cells are, or will be, divided into four or
five subcells.  The purpose of these subcells is to isolate the various waste
groups accepted at  the facility, thereby preventing the interactions of
incompatible wastes.  When five subcells are used, as in cells 1, 2,  3, and
4, the waste categories are as follows:

     «  General wastes.  These wastes represent approximately 44 percent
        of the total waste volume.  General wastes are defined as
                                   7-23

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        materials  of  both  an organic and inorganic nature that do not
        contain  a  significant quantity of any of the other waste
        categories.

             The hazardous acidic or acid-generating materials are
        covered  with  lime  to ensure that any acid that is generated will
        be  neutralized.

      •  Pseudo metals.  This type of material represents approximately 6
        percent  of the total waste volume.  Pseudo metals are arsenic,
        antimony,  bismuth, and phosphorous.  Chalcogens, beryllium, and
        any of their  compounds as well as alkaline-sensitive materials
        are also disposed  in this subcell.

             This  subcell  has a pH buffer system that maintains pH
        levels between 6 and 8.

      •  Heavy metals.  These wastes represent approximately 15 percent
        of  the total waste volume.  This group is comprised of all heavy
        metals and asbestos.  This subcell contains the smallest amount
        of  organic materials, which helps to reduce fire hazards caused
        by  the reaction of strong oxidizing agents with organics.

      •  Highly flammable wastes.  This type of material represents
        approximately 12 percent of the total waste volume.  These
        materials  generally exhibit a flash point between 80 and
        100°F.   These materials are kept apart from powerful oxidiz-
        ing  agents, materials that are prone to spontaneous heating, or
        materials  that react with air or moisture to evolve heat.

      •  Toxic materials.   These wastes represent approximately 23 per-
        cent of  the total waste volume.  Included in this category are
        all highly toxic organic compounds, carcinogens, PCB's, and
        other halogenated wastes.  No solvent-type wastes were permitted
        in this  subcell.

      If only four  subcells are used, the psuedo-metals subcell is eliminated.

7.2.7.5  Liner Description—
     The liners at the five secure land disposal  cells are very similar.
Minor design changes have been made as each cell  was constructed.  The
components of the  liners include:

     e  A minimum of 10 feet of local  and borrow soil  placed above the
        in situ glacial  till.  The soil  is compacted so that the
        permeability is no greater than 1 x 107 cm/s.

     t  An FML.  Both Hypalon® and HOPE ranging from 30 to 80 mils have
        been used.

     •  Cover soil  of 12 to 24 inches  compacted to a permeability of
        1  x 10~7 cm/s or less.
                                    7-24

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      t  In some of the cells, an 8-Inch layer of slag material  placed
         over_the cover soil.  This layer 1s  to provide  a  firm base  for
         equipment movement.

      •  A leachate collection system located on top  of  the  liner  system.
         This system consists of a 12-inch drainage blanket,  slotted
         4-inch geotextile wrapped pipes located 100  feet  apart  (maximum),
         and standpipes or manholes to enable collection and  removal of
         the leachate.

 7.2.7.6  Liner System  Installation--
      Prior to liner installation,  all  of the industrial slag material and
 the organic marsh silt were removed.  The lacustrine clays were not excavated
 because of the high water table.   Dewatering was  conducted as necessary.

      Borrow liner material  was  transported to the facility.  Prior  to liner
 compaction a test patch was required.   This  patch enabled the construction
 contractor to determine the compactive effort necessary to achieve  the
 required permeability.  Density, moisture content, and  permeability measure-
 ments were conducted on the test  patch to establish the ability of  the equip-
 ment to compact the liner to the  design  specifications.

      It was determined  that the  liner  should be compacted 1n 6-inch lifts
 with a sheepsfoot roller.   The  finished  clay liner thickness was 10 feet.
 The sidewalls were Installed in horizontal lifts and cut back to a  final
 slope of 2:1.  The slope  of the bottom liner ranged from 1 to 2 percent.  The
 clay liner was protected  by the FML.   The entire liner  was Installed before
 waste placement was initiated.

      A system of dikes  was  used to  separate  the large cell into the various
 subcells.   The interior dikes were  constructed  in 4-l/2-foot-h1gh sections.
 New sections  of the interior dikes  were  constructed by  keying into  the too of
 the previous  dike (see  Figure 7-8).

      CQA consisted of  soil  density  and moisture content measurements (nuclear
 gauge)  and laboratory permeability  tests  on  undisturbed Shelby tube samples
 of  the  liner.

 7.2.7.7   Performance--
      The  performance of this facility  is  very difficult to determine at this
 time.  A  potential  Superfund site located next to this  facility has caused
 extensive  groundwater contamination  in the area.  For this reason, baseline
 groundwater data  have not been obtained.  However, it 1s known that the
 leachate  removed  from the collection system of the newly constructed facility
 Is  less contaminated than the local groundwater.

 7.2.8  Site G

 7.2.8.1  Physical  Description—
     The facility  consists of several disposal areas  covering 80 acres.   A
 100-acre section  is planned for future development.   Some  sections of the
 landfill are active, while others are capped  (see Figure 7-9).   Each disposal
area is lined and/or capped with unrecompacted local  soil.  A leachate
                                    7-25

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 i
f\3
O)
                                                                       £~~~- Intermittent Creek

                                                                                       r
-it-
                                                                                Leachate Collection System
                                                   Old Drum

                                                 Storage Area
                                                                                     Leachate Collection Tank


                                                                                                           0-
                                                                                                    Monitoring Well
                                                                                                                                N
                                                           Figure 7-9. Plan view of site G.

-------
 collection  system was  installed  in 1982.  Several monitoring wells are
 located within  the area.

 7.2.8.2   Startup Date--
      This site  was first  used as a dump in 1955.  Sanitary landfilling opera-
 tions began in  1967.   A leachate collection system was added in 1982.

 7.2.8.3   Local  Geology and Hydrology—
      This facility is  located in the midwestern United States.  Average
 annual precipitation at this facility is approximately 35 inches.

      The  soil in the vicinity of the landfill is described as silty clay to
 clayey silt, which extends to a depth of 200 feet.  A layer of shale under-
 lies  the  till material.   Discontinuous sand and gravel seams are located
 throughout  the  area.   When encountered, they have been removed prior to
 landfilling.

      Groundwater is known to occur in sand and gravel seams within 6 feet of
 the surface.  The static water level in the clay soil is not known.

 7»2.8.4   Waste  Type—
      The  facility has  accepted various types of hazardous wastes including
 organics, heavy metals, and pesticides.

 7.2.8.5   Liner  Description—
      The  local  soil (unrecompacted) used to line the site has the following
 physical  properties:

      •  Permeability                  1 x 10-7 to 1 x 10-9 cm/s

      •  Natural  moisture content      9 to 12%

      •  Plastic limit                 20 to 21%

      •  Liquid  limit                  11 to 13%

      •  Plasticity index              8 to 10%
                                                    «
      •  Cation exchange capacity      1.2 to 2.0 (milleq./lOO g sample).

7.2.8.6  Liner System Installation—
     This information was not available.

7.2.8.7  Performance--
     Analysis of groundwater samples from well  No.  1 (see Figure 7-9)  has
indicated high levels of lead,  chloride, COD,  total  dissolved solids,
chloroform,  and  various chlorinated organics.

     This contamination is thought to come from an  old drum disposal  site
previously owned by another company located adjacent to the landfill.   The
drum disposal site is located on a sand  and gravel  seam that extends  upward
near the ground  surface.   Contaminants  from this site can reach this
permeable area and travel  southward to  Site G's  monitoring well  No.  1.
                                    7-27

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 Therefore, Indications are that the contamination  1n well  No.  1  has not come
 from Site G._

 7.2.9  Site H

 7.2.9.1  Physical  Description—
      This site has a rectangular 9-acre cell  lined with 4  feet of  locally
 obtained clay that was put down in four lifts.   A leachate  collection system
 composed of 8-inch perforated polyvinyl  chloride  (PVC) pipe  is on  top of the
 clay liner.  Directly below the clay liner are  two lysimeters.   A  third
 lyslmeter is located under the leachate storage basin  (see Figure  7-10).
 The present cell  is filled to near capacity,  and a new cell  is being con-
 structed 1n such  a manner that the bottom clay  liners will be  tied together
 to form one large cell with no vertical  wall  dividing the  old  and  new
 disposal areas.  The presence of lysimeters almost directly  below  the
 leachate collection drain pipes presents a unique  opportunity  to evaluate the
 performance of the intervening layer of clay.

 7.2.9.2  Startup  Date--
      Operation began in December 1980.

 7.2.9.3  Local Geology and Hydrology—
      The facility 1s located in the northern  central United  States.  Averaqe
 annual  precipitation in this area is 30  inches.

      The site 1s  underlain by approximately 50  to  100 feet of dense silty
 sand.  This material  contains boulders,  cobbles, and pockets of  sandy
 material.  The permeability of this glacial till ranges from 1 x 10-* to
 9  x 10-' cm/s. Bedrock is encountered beneath  this layer.  The water
 table 1s at a depth of 50 to 80 feet In  the silty  sand or bedrock.  Ground-
 water flow is primarily in the southeast direction.

 7.2.9.4  Waste Type--
      Wastes accepted at this facility consist of approximately 75 percent
 municipal  and 25 percent paper-mill  sludge.   Small quantities of other
 Industrial  wastes  are  also disposed of at  this facility.

 7.2.9.5  Liner Descrlption—
      The liner system  consists  of 4 feet of recompacted clay underlain by two
 collection  lysimeters.   The  clay for the liner was obtained from a' nearby
 borrow  area.   It consists  of a  reddish-brown to reddish-gray sllty clay.   The
 specifications  for the material used were as follows:

      •   Liquid  limit             >30%

      §   Plasticity Index         >15%

      •   P-200                    >50%

      •   Permeability             
-------
1
*•*
Under
Construction


o


1
1L1
\

Active
i
i
\
\
U— Drain
i Pipe
i
I
|t2 ^
^s J
—":.•'..'. ...•'.•- - - . . ^*^
a i









^
'
-,
^

ft
-
'

-
1







Road
/

P
1 _»
rn no" r-
j      I
        Leachate
        Storage
         Basins
                                              •f
                                                      M
                                   Single Monitoring Well
                             -<>-   Monitoring Well Nest
                              a    Lysimeter Sump
                              o    Piezometer
                             ^=»   Lysimeter Area
Figure 7-10. Plan view of site H.
          7-29

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Silty Sand
Protective
Layer
Sand
1% Slooe \

' >
T

t
5'
ElS
x 8" Perforated Pipe Le

X \*% ;^****?T * , * ";"
a-^^ t
4'
Clay Liner i
2 . 	 1 	
lachatc
Rock


\\
        Lysimeter


   20 mil PVC Sheeting
               \\
      Sand


4" Perforated Pipe
     Figure 7-11. Cross-sectional view of site H liner showing details
       of leachate collection system and lysimeter construction.
                           7-30

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     The  leachate  collection  system consists of a 1-foot trench excavated
 into 5-foot-thick  sections of the clay liner.  Eight-inch perforated PVC pipe
 is  positioned  in the  trench,  which is backfilled with 3/4-inch crushed rock.
 The entire  trench  is  overlain by a 2-foot-high mound of sand.  A 1-foot-thick
 layer  of  silty sand covering  the entire bottom of the landfill serves as a
 protective  layer for  the clay liner (see Figure 7-11).

     The  lysimeters located under the clay liner are approximately 12 feet by
 100 feet.   They are lined with 20-mil PVC sheeting and filled with medium to
 coarse sand.   Four-inch perforated PVC pipe positioned in the bottom of each
 lysimeter (see Figure 7-11) connects them to a manhole, thus enabling
 leachate detection and collection.

 7.2.9.6  Liner System Installation--
     Prior  to  clay liner installation, the fill area was rough graded.  Clay
 was brought to the facility from a nearby borrow area.  The variable nature
 of  the borrow  area required a soils technician to be present during all
 removal operations to ensure  that the material met the project specifica-
 tions.  The technician rechecked the material by performing the required soil
 tests as the clay was emplaced.  The liner was compacted in 12-inch lifts
 with either a  rubber-tired or sheepsfoot roller.

     The construction quality control  (CQC) program called for 29 Shelby tube
 samples taken  at various locations in each of the four 1-foot-thick clay
 lifts.  These  samples were tested for various parameters.  The results of
 these tests were:

     •  Permeability             7 x 1Q-8 cm/s, 5 x 10-10  Cm/s

     0  Liquid  limit             39 - 82%

     0  Plastic limit            20 - 37%

     0  Plasticity index         16 - 54%

     0  P-200                    >50%

     0  Density                  92 - 102.8% of maximum dry density
                                  (nuclear gauge)

                                 95 - 110.8% of maximum dry density
                                  (sand cone).

 7.2.9.7  Performance--
     Quarterly sampling of all monitoring points began in December 1980.
This sampling  included determining leachate volumes and composition,
 lysimeter liquid volumes and composition, and groundwater composition.  The
 liquid volumes collected from both the lysimeters and the leachate collection
system are shown in Table 7-3.
                                    7-31

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                              TABLE 7-3.  LYSIMETER  (L) AND LEACHATE COLLECTION SYSTEM (LCS)
                                             LIQUID  VOLUMES (GAL) AT SITE H
Date
Lia
12
L3
LCSb
12/80
38
66
Dry

3/81
24
9.4
1
NA
6/81
1.9
0.6
Dry
NA
9/81
0.03
0.03
1
89,603
12/81
Dry
Dry
0.75
NA
3/82
Dry
Dry
Dry
NA
6/82
Dry
Dry
Dry
32,995
9/82
Dry
Dry
Dry
63,321
12/82
Dry
Dry '
Dry
89,678
12/83
	 1 —
Dry
Dry
Dry
NA
       <*Lysimeter 1 is located below the leachate holding pond.
       bThe numbers indicate the total monthly volume of leachate that was pumped  from  the collection  system at
        irregular intervals.
CO
N>
       NA = Data not available.

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      As Table 7-3 Indicates, the volume of liquid collected 1n Ivsimeters  ha Placed 1n two of the  ponds  that  fa11  but was not
 placed in the third pond until  the following spring.

 7.2.10.3  Local  Geology and Hydrology —
 c* 4.  Tn1snfac11ity  Is located in a semiarid section  of the western United
 States.  Average  annual  precipitation at the facility is approximately
 lo inches.                                                           J

      Approximately  75 percent of the site area was used for  the land applica-
 tion  of sewage sludge.   This  material  was disked  into the top  layer of so}}

 7°f2ro? ?^?f J3yr  °f -I9"1* °rgan1c topso11'  Below tn1*  layfir lies  5  to
 7 feet  of residual  clay  soil  underlain  by 5  to 20 feet of sandstone, which

                       of clay  stone  bedrock-  The
      o   Liquid  limit                  36 to 57 (average  45) %

      «   Plasticity index              is to 27 (average - 21) %

      i>   Natural water content         14.6 - 26.1 (average - 23)  %

      •   Dry density                   80.9 (1 sample)  Ib/ft3

      '   PH                            7.5 - 7.7 (average - 7.6)

      •   Unified Soil  Classification   CH, CL, and CL-CH.
         System designation

     The groundwater at the site ranges  from 100  to  200  feet below the
surface.  Drainage across the site is to the east.

7.2.10.4  Waste Type—

n»Ci--I?S thrK6 E°ndf  nave received most  types of  hazardous waste,  except
pesticides, herbicides,  PCB's,  dioxin, reactive materials, and any material
                                   7-33

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TABLE 7-4.  MONITORING DATA FOR SITE H
Parameter
Sample date
Chloride (mg/L)
COD (mg/L)
pH
Alkalinity, total
(mg/L)
•jj Conductivity
u (micro/cm)
Total hardness
CaCO (mg/L)
Iron, dissolved
Baseline
groundwater
analysis
6/80
1.5 -
4.0 -
7.2 -
120 -
300 -
122 -

0.49 -
5.4
21.0
7.6
240
385
228

2.65
Upgradient
well
9/81
2.5
11
7.4
206
405
222

0.06
Range for
all other
wells
9/81
1 -
4 -
7.2 -
150 -
320 -
162 -

0.01 -
3
50
7.4
168
350
182

0.09
Leachate
6/81
230
5,315
6.1
960
5,000
3,650

161
Range for all
lysimeters
i —
6/81
16 -
40 -
7.1 -
291 -
625 -
344 -

0.06 -
19
57
7.2
445
840
480

0.20

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 containing more than 5 percent  solvents.   Pond No.  1 was the only pond to
 receive oily-wastes.

      Wastes were placed in  the  ponds  through a trough leading to the base of
 each  pond.

 7.2.10.5  Liner Description—
      The liner at this facility consists of two 5-foot layers of recompacted
 local  clay soil  that are separated by a 15-inch leak detection layer.  The
 three ponds are separated by dikes that are 12 feet wide at the top (see
 Figure 7-12).   The interior slopes of the  dikes (sidewalls) are 3:1.  A
 cross-sectional  diagram of  the  liner  system is illustrated in Figure 7-13.

      Properties of the local clay soil that was used as the liner material
 are  listed in  Section 7.2.10.3. Additional laboratory testing of this
 material  indicated that it  had  a permeability ranging from 2 x 10~9 to
 4.8 x 10-° cm/s.  ^e value for the permeability of the claystone
 material  ranged from 3 x 10~9 to 1 x  lO'8  cm/s.

 7.2.10.6  Liner System Installation—
      The local  soil  was excavated with dozers and scrapers.  Excavated clayey
 materials were placed on a  stockpile. Here the material was spread in 8-inch
 lifts and then watered to achieve a moisture content between optimum and
 3  percent above optimum. After the excavation was complete, the pond bottoms
 were  graded according to design specifications.  This included the additional
 excavation of  a 10-foot-wide trench area beneath the leak detection system
 collection pipes.

      The  stockpiled  liner material was disked and then placed in the pond
 excavations in  horizontal lifts (which, before compaction, were 8 inches
 thick).   The lifts were compacted to  95 percent standard Proctor density with
 a  sheepsfoot roller.

     A backhoe was used to  excavate a shallow trench into the bottom liner
 for the  leak detection  drain and sump.  Perforated pipe was placed in the
 trench and  then  covered with gravel.  The entire bottom liner was then
 covered with a  sand drainage layer.

     The  final 5-foot  (minimum) clay  liner was constructed through the same
 procedure as previously discussed.  A 2-foot protective layer of sandy soil
was placed  on top of  the  finished clay liner.   Waste unloading troughs were
 protected at the bottom with rip-rap.

7.2.10.7  Performance—
     The construction of  the liners of these ponds  was  completed in  the fall
of 1980.  Ponds No. 1 and 3 were filled with waste  shortly thereafter.   Pond
NOo 2, however, was left  unfilled and uncovered  until  the  following  spring.
Approximately 3 months  later,  liquid started accumulating  in  the leak
detection system.  This  liquid  had elevated levels  of  chloride,  ammonium,  and
total  dissolved solids as well  as increased conductivity.   Liquid  was  not
detected in the sumps of ponds  No.  1  and 3.
                                    7-35

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CO
0>
                                                               Figure 7-12. Pian view of site !.

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CO
VI
             Truck Maneuvering Area   ^^-18-in Gravel Layer

                                                     Freeboard
                                                                                 Waste
                                                                   2 ft Liner Protection Layer
                                         10 ft (max.)
                                         Liquid
                                         Depth
                                                                 18-in Leak Detection Layer
                                               5 ft (min.)
                                          Compacted Clay Liner

                                                                  5 ft (min.)
                                                             Compacted Clay Liner
                                      Leak Detection Pipe
\\
                                                                     \\   //   \\
\\
\\
                                                                                                 10ft
                                                     Figure 7-13. Cross section of liner at site I.

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      The most probable cause of the failure at pond  No.  2 was waste migration
 through desiccation cracks in the upper liner.  Cracks  ranging  from 2  to
 10 mm wide were observed on the upper portion of the sidewalls.   In most
 cases, these cracks could not be traced for any more than a  few feet along
 the surface.  An exception to this was in the corners of the liner, where the
 cracks appeared to be up to 20 feet long.

 7.2.11  Site J

 7.2.11.1  Physical Description--
      This facility consists of a drum disposal  pit,  a solvent recovery facil-
 ity,  and seven ponds, one of which is used for landfill ing.  The  ponds range
 from  approximately 1/2 to 4 acres.  All  of these areas are lined  with two
 layers of compacted clay separated by a leak detection system.  A 10-foot-
 high  retention dike located northeast of the disposal areas  prevents any
 overflowing liquid, such as may occur during a 100-year  storm,  from leaving
 the facility.  Several  groundwater monitoring wells  are  Installed around the
 facility (see Figure 7-14).

 7.2.11.2  Startup  Date--
      Ponds No. 1 through 4 and the drum pit  went into service in  June of
 1979.  The remaining ponds (No. 5 and 6)  started operation in May of 1981.
 Pond  No. 7 was used as  a landfill  starting in May of 1981.

 7.2.11.3  Local Geology and Hydrology—
      This facility is located in  the southern central United States.  The
 average annual  precipitation at the facility is  approximately 26  inches.

      The top layer of soil  at this site  consists  of  red  silty clay.  Thin
 sandstone and gypsum lenses are present  at depths ranging from 8  to 18 feet
 below the ground surface.   A layer of gray siltstone  encountered  at depths
 ranging from 14 to 27 feet underlies the  silty clay.  The physical properties
 of  the silty clay  are as follows:

      • Soil  type                           Very fine  silts or clays

      •  Liquid limit                      31.0  - 46.0%

      •  Plastic limit                     22.3  - 29*5%

      •  Plasticity Index                    7.4  - 20.1%

      •  Optimum moisture content           18.0  - 23.7%

      •  Maximum dry density               99.3 - 110.4  lb/ft3

      •   Laboratory permeability            2.0 x 10-9 _ 2.9 x lO'8 cm/s.

      Six  borings were dug  in an attempt to determine the location of the
water  table.  At the  time of exploration, water was encountered  in two  of the
borings at depths  of  7 and approximately 27 feet below the  ground surface.
Ten days  later, water was standing  in all six borings at depths  ranging from
5 feet 8  Inches to 23 feet below the ground surface.   Surface drainage  from
the site  is  in two directions—north and east.
                                    7-38

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VI
I
CO
tO
                        Groundwater
                           Flow
                                                                                             Solvent
                                                                                             Recovery
                                                                                             Facility
                                                           Figure 7-14. Plan view of site J.

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 7.2.11.4  Waste Type--
      Th1s facility receives most types of hazardous  liquids and  sludges.

 7.2.11.5  Liner Description—
      The bottom liners at this facility consist  of two  recompacted clay
 layers separated by.a leak detection system.   The lower clay  liner is  1 foot
 thick and the upper clay liner is a minimum of 5 feet thick.  The sidewa'lls
 are constructed partially underground and partially  above ground.  The above-
 ground sections are built upon dikes.  The leak  detection system is a  6-inch
 drainage blanket that slopes to a trench containing  a 2-inch  slotted PVC
 collection pipe (See Figure 7-15).  Quality assurance test results of  the
 completed liners are as follows:

      •  Dry density                   94.2 -  115.8 Ib/ft3

      •  Moisture content              15.8 -   31.0%

      e  Permeability                   5.3 x  1Q-9 -  2.8 x 10-Q cm/s

      •  Liquid limit                  35.6 -   63.0%

      •  Plastic limit                 16.1 -   31.6%

      •  Plasticity index               6.7 -   36.6%.

 7.2.11.6  Liner System Installation--
      No  specific information on the liner construction  or the equipment used
 was  available.  However,  it is  known  that construction  of the second phase
 (ponds No.  5,  6,  and  7)  took place during the  winter.   Problems due to frozen
 and  unworkable liner  materials  caused many construction  slowdowns.

      Quality control  (QC)  and  quality assurance  (QA) inspectors were present
 at the facility during  construction operations.  They conducted tests, made
 observations,  and prepared a project  diary and final documentation report.

 7.2.11.7  Performance--
      Liquid,  presumed to be construction  water, was being collected and
 removed  from all  of the detection  systems  by early 1982.  This liquid was
 periodically analyzed and  found  to  be "clean"  until  February 1982.  At this
 time,  samples  removed from the  pond No. 5  detection system contained a
yellow-brown oily liquid with an organic-solvent odor.  A small  water phase
was present  in  the sample.   Analysis  of this sample showed that 1t contained
 over  11.2 percent perch!oroethylene (perc)  plus small amounts of other
 chlorinated  and  nonchlorinated  organics.  The  facility was allegedly not
 accepting wastes  with more  than a  trace of  "perc."

     An  Investigation of the problem  revealed that aqueous wastes coming from
 one of the disposal facility's  customers  contained approximately 5 percent
degreasing fluid  waste, which contained perchloroethylene.  This waste was to
 have been stored  in a separate  tank at the originator's plant.  Evidently, it
was not made  clear to the workers where to put the  "perc" waste,  and it was
placed 1n an aqueous waste  storage  tank.  Being insoluble and heavier than
                                    7-40

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Dike
                                          2    Sidewall Slope
                                            I/
                                                                                  2-in Slotted PVC
                                                                                  Leak Detection Pipe
               5 ft (min.)
               Compacted Clay
               Liner
                 6 in Drainage Blanket
                 (Leak Detection System) •

                  1-ft Compacted Clay Liner
6-in (min.)
                               Figure 7-15. Cross-sectional view of site J liner.

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water,  1t sank to the bottom.  When a tank truck from the disposal facility
would collect a  load of aqueous waste, it would also receive a few hundred
gallons of tfie "perc" waste.  The waste sampling method used by the disposal
facility on all  loads of incoming waste was not able to sample the bottom few
inches  of each load.  In addition, the parking area where all truckloads of
waste were sampled was slightly sloped; this sloping caused the relatively
small amount of  "perc" waste in the bottom of the tanker to flow to the back
of the  truck, where it could not be reached by the sampling device.

     Over approximately 9 months, the aqueous waste containing the "perc" was
placed  in one of the clay-lined ponds and went unnoticed until the liner
failure occurred.  The apparent incompatibility is consistent with current
research on the  effects of chlorinated solvents on clays.

     Presently,  the leak in the pond No. 5 liner has slowed down consider-
ably.   Perch!oroethylene concentrations in the detection system liquid are
less than 100 ppm.  It is estimated that several thousand gallons of the
"perc" waste are adsorbed into the clay liner and the sludges in the pond's
bottom and will  present minor problems for many years.

7.2.12  Site K

7.2.12.1  Physical Description—
     This facility consists of six double-lined ponds ranging in size from
1.2 to 2 acres.  The liners are composed of a 3-foot recompacted clay layer,
below which lies a leak detection system and a 1-foot layer of recompacted
clay.  A typical cross-section of the pond and liner system is illustrated in
Figure 7-16.  The design depth of all six ponds is 10 feet.

7.2.12.2  Startup Date—
     The construction of the first pond at this facility was completed in
December 1981.   Five additional ponds have been constructed since then.

7.2.12.3  Local  Geology and Hydrology™
     This facility is located in the western United States.  Average annual
precipitation at this facility is approximately 6 inches, while the average
annual evaporation is 63 inches.

     A total of  10 trenches and 12 borings ranging from 8 to 100 feet in
depth were used  to investigate the geology at this facility.  This investiga-
tion, combined with prior knowledge, revealed three distinct layers of silty
claystone, siltstone to sandstone, and silty claystone.  The uppermost layer
caps a flat ridge at the facility.  Here the silty claystone is up to 80 feet
thick.  The next layer ranges up to 120 feet thick.  The lower layer is in
excess of 80 feet thick across the entire site.

     The uppermost claystone layer was characterized most extensively.  It
has the following properties:

          •  Liquid limit                  56 - 84%

          0  Plasticity index              36 - 55%

          e  P200                          83 - 99%
                                    7-42

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VI
I
CA>
                                                    Waste
            10ft
                               \\
\\
•   _       • •• ' _L^M,
  /A           K^N
 //\     3ft  St
    ^^^	J	
\\
                                                                  \\
                                                                                 1% Slope
                            1% Slope
                                                                                                                        Dike
                                                                                                                 3 ft (min.)
                                                                                                                 Recompacted
                                                                                                                 Clay Liner
\\   //   \\   .
 1 ft (min.)
 Sand Basket
 (Leak Detection
 System)
                                                                                              1-ft (min.)
                                                                                              Recompacted Clay Liner
                                                                              4 in Slotted PVC Pipe
                                                 Figure 7-16. Cross-sectional view of site K liner.

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           t  Laboratory permeability       5.0  x  10~7 - 2.8 x  lO"8 cm/s
                  (remolded)

           •  Laboratory permeability       3.7xl07-6.1x  lO"8 cm/s
                  (undisturbed)

 Investigations also revealed the  presence  of  occasional gypsum veins through-
 out the claystone material.   These  veins ranged in thickness from less than
 1/10 inch to about 3 inches  and had an  average  permeability of
 2.4 x 10-3 on/s.                            a            y
      A review of published  data  indicated  that  several seismic faults exist
 in  the region of the disposal  facility.  However, within 4 miles of the site
 no  seismic faults show evidence  of  recent  creep.  The two seismic faults
 within 1/2 mile of the facility  are both inactive.

      State investigations indicate  that groundwater  is scarce in the vicinity
 of  the site.   This fact was confirmed by drilling 12 borings on the site
 property.   Of the 12,  only  1 encountered water  at a depth of 32 feet perched
 on  claystone  bedrock.

      The scarcity of groundwater is due to  low  rainfall, high evaporation,
 and the fine-grained nature of the  sediments.

 7.2.12.4   Waste Type--
      The facility accepts liquid-scrubber wastes that are generated while
 stack gases are cleared from oil-refining facilities.  The wastes are highly
 saline with pH values  in the wide range of  3.5  to 9.0.  The waste is
 temporarily stored in  the evaporation ponds.  When it has been reduced to a
 semlsolid,  it is removed and disposed of onsite.

 7.2.12.5   Liner Description—-
      The pond liners were constructed of the local excavated claystone
 material.   The liner system consists of a 1-foot recompacted basal  liner.
 Sump  and collection  trenches are excavated  into this bottom liner.   A 1-foot
 sand  layer  covers  the  lower clay liner.  The sand layer is overlain with
 3 feet  of  clay.

      Four undisturbed  samples were  taken from one of "the constructed liners
 and tested  for their Atterberg limits, percent passing the No.  200  sieve,
moisture content, and dry density.  The results of these tests  are  presented
 below.
                                      _L       2       _3 _       4

     •  Atterberg limits

          -Liquid limit (%)            70        87        84        93

          -Plasticity index  (%)       49        67        64        69

     t  Amount passing No. 200         86.9       88.1       88.3       87.2
          sieve  (%)
                                    7-44

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      •  Moisture content (%)           24.9       21.5       20.8      23.0

      •  Dry density (Ib/ft3)           94.6      103.0      104.4      99.8

      Permeability tests were  conducted in which  remolded  liner  samples were
 subjected first to water and  then  to  typical wastes.  The permeability of the
 liner material  to both  water  and the  scrubber waste ranged from
 2  x ID-7 to 1  x ID-8 cm/s.  The design specifications called for the
 liner permeability to be no greater than 1 x lO'6 cm/s.

 7.2.12.6  Liner System  Installation—•
      The leak  detection system was constructed by first excavating and sub-
 sequently recompacting  the clay soil to provide  a 3-foot  foundation beneath
 the collection  drains and sump.  A 1-foot clay liner was  then placed over the
 base and side  slopes of the excavated  area.  The sump and  drain-pipe trenches
 were then excavated over the  3-foot foundations.  After the installation of
 the drainage system,  a  1-foot layer of sand was  placed over the entire clay
 liner.   Finally,  a 3-foot recompacted  clay liner was placed on  top of the
 sand layer.  A  segmented steel-wheel compactor was used for liner
 compaction.

      Construction  activities  were inspected by the design  firm.  Included in
 these inspections  were  numerous density, moisture content, and  permeability
 tests.   At  the  completion of  construction, the design firm certified that the
 facility was constructed according to  design specifications and would there-
 fore perform as  designed.

 7.2.12.7  Performance--
      Liquid volumes  collected in the leak detection system were used to
 determine the  installed liner permeability.  The permeabilities for five of
 the six  ponds were calculated based on Darcy's Law, the collected leachate
 volumes,  and the  impounded liquid depth and pond area.  The value for pond
 No.,  4 was not available.  These values are as follows:

                Pond                  Average Permeability  (cm/s)

                  1                         2.95 x ID'7
                                                    *
                 2                         1.8 x 10-7

                 3                         4.1 x ID'8

                 4                         Data not available

                 5                         1.4 x 10-7

                 6                         1.4 x 10-7

     The permeability of the installed liner system is less than the
specified value of 1 x 10~6 cm/s.
                                    7-45

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      This facility 1s located approximately 100 miles  south of the epicenter
 of a recent major earthquake.  After the quake, the  excavation, slopes, and
 berms were examined carefully, but no indications  of seismic damage were
 noted.  Careful  monitoring of the ponds  since  the  quake  has not revealed any
 unusual  changes  in fluid levels or leachate collection volumes.

 7.2.13  Site L

 7.2.13.1  Physical Description--
      The landfill  consists of a flat double-clay liner on top of which a dike
 has been placed  to contain the wastes.   The liner  extends beyond the dike to
 form the liner for a 12-foot-wide drainage  ditch that  encircles the site (see
 Figure 7-17).                                                           v

      The landfill  is divided into two separate sections, one for each of two
 types of waste.   The largest area is designed  to contain dewatered sludge
 pumped from settling tanks.  It has a 5-foot-high  perimeter dike and a
 drainage blanket on top of the liner composed  of 1 foot  of graded clean sand
 with drain pipes installed to collect and remove leachate.  Sludge is
 transferred to this portion of the landfill  through  a  pipeline from offsite
 settling tanks.

      The smaller section of the landfill  is designed to  hold chemical wastes
 from the plant manufacturing units and QC laboratory.  It has a gravel bottom
 over its liner.   The working area was developed in sections across the width
 of the landfill  with the waste layer maintained at approximately 3 feet in
 depth.  Each 11ft  of waste was covered with river  sediment material
 previously deposited on the site.

 7.2.13.2  Startup  Date—
      The site became active in 1978.

 7.2.13.3  Local  Geology and Hydrology--
      The facility  is located in  the northeastern United States.  Average
 annual precipitation at this facility 1s  approximately 40 inches.

      The facility  is located in  an  area where  there  is approximately 3 feet
 of topsoil  over  a  subsoil  varying  from silt  to sand  to fine gravel  and sandy
 clay.  Groundwater is located  in  the  subsoil layer a* depths ranging from 4.5
 to 14.5  feet  below the  ground  surface.

 7.2.13.4 Waste  Type--
     The landfilled  waste material  can be defined as either sewage  treatment
 plant  sludge  or  chemicals;   The  sewage treatment plant sludge consists of
 dewatered  (12  to 15  percent  solids) sludge removed from settling  tanks and
 transferred to the  landfill.   The chemical waste consists of Inert  material
 from Hme slaker operations  (inert  rocks and insoluble calcium and  magnesium
 salts),  hard-pitch  residue  that  is only slightly water soluble and  that
 crystallizes at  180°C,  filter  aid  (dicalite) wetted with  phosphate
 esters,  filter paper wetted with phthalate esters,  and residue from the
manufacture of tetrachlorophthalic anhydride.
                                    7-46

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VI
 I
                Waste
Dike
                                                          Drainage Layer
                                                               Leachate Collection Pipe
  Leak
Detection
  Layer
                                             Figure 7-17. Cross-section of containment system at site L.

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7.2.13.5  Liner Description—
     The liner system at this facility consists of the six layers listed
below from the top down:
     t  8- to 12-in. drainage layer (sand or gravel)
     •  18- to 25-ini compacted clay
     •  12-in. sand leak detection layer
     •  12-in. compacted clay
     •  6- to 18-in. compacted soil
     •  Bidim type C34  (synthetic soil stabilization  geotextile).
     The physical properties of the clay used for the liner are as follows:
     •  Soil classification - grey silty clay
     0  Particle size distribution:      Gravel - 1%
                                         Sand - 29%
                                         Clay and colloids - 707.
     •  Liquid limit                     45%
     0  Plastic limit                    17%
     0  Plasticity index                 28
     0  Liquidity index                  0.1
     0  Specific gravity                 2.67
     0  Moisture content                 28.5%
     0  Dry unit weight                  95.0 lb/ft3
     0  Maximum dry density              101.5       *
     0  Optimum moisture content         19.5%
     0  Permeability      .               6.6 x lO"8 to 3.8 x 10'9 cm/s.
7.2.13.6  Liner System Installation--
     No information was available on installation procedures.
7.2.13.7  Performance™
     Within the first year of operation, problems developed in the upper  clay
liner.  Evidence of this was the appearance of contaminated water in the
leachate monitoring layer manhole.  Slight contamination in local groundwater
monitoring wells was also discovered.  A study conducted to determine the
source of the groundwater contamination revealed that the source of contami-
nation was not the double-lined pond.
                                    7-48

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 7.2.14  Site M

 7.2.14.1  Physical Description—
      This 12-acre site is designed to consist of three cells  of approximately
 equal size.  At the time of this writing,  the first cell  was  still  in  use  and
 construction had not yet started on either of the remaining two cells.

      The facility is lined with 1 foot of  recompacted clay.   A leachate
 collection system is above the clay liner  and a leak detection system  lies
 2 feet below the clay liner.  In addition  to the leachate collection and
 subsurface monitoring (leak detection) systems, three groundwater monitoring
 wells are situated around the facility as  well  as drainage ditches  to  prevent
 surface runoff from entering the landfill  (see Figures 7-18 and 7-19).

 7.2.14.2  Startup Date—
 10-70 Construction was initiated 1n 1977.   The first wastes were accepted in
 1978 ii

 7.2.14.3  Local  Geology and Hydrology—
      This facility is located in the northern central  portion of the United
 States.  Average annual  precipitation in the vicinity of  this facility is
 approximately 26 inches.                                            *

      A total  of  five borings were used to  investigate the subsurface
 conditions at the proposed landfill  site.   The  borings indicated a  uniform
 geologic profile over the entire facility.   The top 1  to  2 feet  of  soil
 consists of a sllty sand underlain by approximately 25 feet of fine- to
 medium-grained sandy alluvium.

      Groundwater was encountered in  all five  borings  at depths  ranging from
 approximately 10.5 to 15 feet below  the original  ground surface.  Groundwater
 flow was toward  a marshy area located east  of the proposed facility.  Other
 information  indicates that in a  second deep aquifer groundwater  flow is in a
 southeasterly direction.

 7.2.14.4  Waste  Type and  Placement--
      The landfill  is used  for the disposal  of inorganic lime sludge. Samples
 of the  sludge have been  analyzed for  heavy metals content and percent solids.
 The  results of these analyses are presented in Table*7-5.

     Due  to the  high moisture content of the waste material,  a special  proce-
dure for waste placement was  developed.  This procedure involved mixing a
thin  layer of  the  sandy soil  obtained from the site excavation with  a thin
layer of the waste  1n order to reduce the overall moisture content and  to
give the material  structural  stability.  The range of soil to  waste  ratios
varied from 0.5:1  to  1.5:1.  Exact mixing proportions were determined in  th«
field and judged sufficient when the landfill equipment was able to  drive
over the mixture.  Due to the great amount  of soil mixed with  the waste and
the waste's inorganic nature, no dally cover was used at this  facility.  The
proposed final cover will consist of a 6-inch compacted clay  cap, 2  feet  of'
topsoll, and a vegetative cover.  No gas venting or collection will  be
necessary.
                                    7-49

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en
o
                                            Original Ground Contour
1ft
Coarse
Sand or
Fine Gravel
                        Subsurface Monitoring
                        System Pipe
                        (Leak Detection)
                                   Leachate
                                   Collection
                                   System Pipes
                                       1-ft Compacted
                                       Clay Liner
Leachate
Collection
System Sump
and Manhole
Subsurface
Monitoring
(Leak Detection)
System Sump
and Manhole
                                                        Figure 7-18. Cross-section of site M.

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                                                         O  Location of borings
                                                             Location of monitoring wells
                                                        MH  Manhole
                      Area for
                Future Development
                                  Direction of
                                  Groundwater
                                  Flow
                                                         Leachate Collection System
                                                         Perforated Pipes
                                                                      Subsurface
                                                                      Monitoring
                                                                      System (Leak
                                                                       Detection)
Figure 7-19. Plan view of site M leachate collection and leak detection
                                                                 systems.
                                 7-51

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                            TABLE  7-5.   HEAVY  METAL  CONTENT AND PERCENT SOLIDS OF LIME SLUDGE
                                                     DISPOSED AT SITE M


Sample date
7/79
7/80
10/81
7/82

Cadmium
(mg/kg)
6.6
1.6
3.3
0.89

Chromium
(mg/kg)
200
110
1,300
170

Copper
(mg/kg)
4,500
5,300
3,800
520

Cyani de
(mg/kg)
750
140
2
52

Iron
(mg/kg)
5,400
10,000
11,000
880

Lead
(mg/kg)
5,200
5,100
4,800
520

Nickel
(mg/kg)
1,300
1,100
340
64

Zinc
(mg/kg)
5,700
4,900
5,200
640


PH
7.8
8.6
7.9
8.5
Total
sol i ds
(%),
—
11.1
28.7
12.1
01
ro

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 7.2.14.5  Clay Liner Description—
      The clay for the liner was obtained from a  nearby  borrow area.  The
 specifications for the clay are as follows:    ?

      t  Liquid limit        50 - 70%

      t  Plasticity tndex    >28%

      •  P200                >75% (by weight)

      •  Permeability        
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                             TABLE  7-6.   GROUNDWATER MONITORING WELL SAMPLE ANALYSIS  AT SITE M
VJ
I
U1
Well
number
1
1
2
2
3
3
Sample
date
7-79
7-82
7-79
7-82
7-79
7-82
Cadmium
(mg/kg)
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
Chromi urn
(mg/kg)
<0.05
<0.05
<0.05
<0;05
<0.05
<0.05
Copper
(mg/kg)
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
Cyani de
(mg/kg)
<0.01
<0.02
<0.01
<0.02
<0.01
<0.02
Iron
(mg/kg)
0.30
0.10
0.25
0.4
0.1
0.05
Lead
(mg/kg)

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      The leachate from the landfill has also been sampled and analyzed since
 1978.  Examples of these data appear in Table 7-7.

      The subsurface monitoring system tank also has been checked on  a
 quarterly basis.  There has been no indication of leachate entering  this
 system.

      The above facts confirm that the landfill has performed as  designed
 since its construction and initial  waste placement in  1977 and 1978.

 7.2.15  Site N

 7.2.15.1  Physical Description—
      The site is located in an old  sand and gravel  pit and covers
 approximately 160 acres.  The eight cells range in size from 9 acres to 25
 acres with 20 acres being the average cell  size.   At the time of writing, the
 liner covers 108 acres.

      The facility bottom is lined with a 4-inch bentonite and sand
 layer.  The sides of the landfill are unlined.  Two 1,000-ft2 PVC-lined
 lysimeters are below the liner as well  as a system of  24-inch perforated
 pipe, which lowers the groundwater  table.  A leachate  collection system is
 above the liner.  In addition to these systems, several  monitoring wells and
 surface-water monitoring points are around  the facility (see Figures 7-20 and
 7—21)*

 7.2.155.2  Startup Date-
      Construction of cell  1 was initiated in 1974.   Since then,  seven
 additional  cells have been installed.

 7.2.15.3  Local  Geology and Hydrology—
      This facility is located in southeastern  Canada.   The average annual
 precipitation in the vicinity of the  landfill  is approximately 35 inches.

      Very little information  was available  concerning  the  local geology and
 hydrology.   As previously  mentioned, however,  the facility is  located  in an
 old  sand  and gravel  pit.   The local soil  is  very sandy and,  for this reason,
 a  bentonite  liner  was chosen.
                                                     «
      Because natural  groundwater elevations  at  the facility are very near the
 surface,  a drainage  system was  installed  to  lower the groundwater table.  The
 final groundwater  elevation is maintained at 5  feet below the liner bottom.

 7.2.15.4  Waste Type—
      The  facility accepts municipal  solid waste only.  At the time of
 this writing, the facility contained approximately 25 million yd3 of
waste material.

7.2.15.5  Liner Description-
      Laboratory studies have shown that 6 percent by weight of bentonite
 (sodium montmorillonite with 55 to 75 percent by weight passing the  No. 70
mesh sieve)  in a 6-inch sand layer would produce a liner with the specific
                                    7-55

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                                           TABLE 7-7.  LEACHATE ANALYSIS  AT SITE M
Sample date
7/79
7/80
10/81
7/82
Cadmium
(rag/L)
<0.01
<0.01
<0.01
0.02
Chronri urn
(rag/L)
<0.05
<0.05
<0.05
0.05
Copper
(mg/L)
0.15
0.20
0.30
0.35
Cyarri de
(mg/L)
0.02
0.03
0.09
<0.02
Iron
(mg/L)
3.5
4.0
3.0
3.5
Lead
(mg/L)
<0.1
<0.1
0.1
<0.2
Nickel
(mg/L)
0.10
0.05
0.35
0.15
Zinc
(mg/L)
0.13
0.10
0.10
<0.10
PH
'7.4
7.5
6.9
7.2
VI
I
en
o>

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 I
01
                                                 Groundwater
                                                 Pumping Station
                                                       Figure 7-20. Plan view of site N.

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en
oo
Groundwater
  Pumping   Lysimeter
   Station     Manhole
                                         Leachate
                                         Pumping
                                          Station
                                                               Vii'".£'i::iu'.'lii'i-'°il>•'—'&:'£'''^'''£-&Zy/\'-'.*.\'':'?;
                                                                                 6 in Sand Layer
                                                                                 (Collection System)
                                                                                                       } Bentonite-Sand Liner
                                                                                                    Lysimeter
                                                                                                    20 mil PVC Membrane
                                                                                                    Lysimeter Drain Pipe
                                                                             Perforated Groundwater
                                                                             Drain
                                                                                          Compacted
                                                                                          Native Sand
                                                                                          18 in (min.)
                                    Figure 7-21. Cross-sectional view of site N liner and ieachate management systems.

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 permeability of 1 x 10-8 cm/s.  Duping liner installation, a 4-inch layer
 produced a moje uniform mix.  Therefore, a 4-inch liner was installed with  an
 additional 3 percent by weight of bentonite as a safety margin.  The liner
 was compacted to a minimum 90 percent standard Proctor density.

 7.2.15.6  Liner System Installation—

      7.2.15.6.1  Excavation—Little additional excavation was necessary due
 to the location of the facility in an old sand and gravel pit.  Areas that
 were to be lined were excavated to bottom contours and graded to a 1-percent
 slope with large-capacity self-loading scrapers.  A 7-ton, self-propelled
 vibratory, smooth-drum roller was used to compact the basal  sand and to
 complete the grading of the cell  bottom into a relatively smooth surface.

      7.2.15.6.2  Liner—The following methods were used to construct the
 liner.

      Bentonite was spread to a 5/8-inch thickness with three to five passes
 of a large scraper.   Next,  a tractor-mounted rotatiller was  used to mix the
 bentonite into the sand to  a depth of approximately 4 inches.   The liner
 material  was allowed to hydrate naturally.   Additional  water was added  as
 necessary to achieve the required moisture  content.   The liner was compacted
 with a vibratory smooth-drum roller a minimum of four passes.

      The  leachate  collection system was  then installed  on  the  liner and
 covered with clean pea  gravel.  A 6- to  8-inch  layer of loose  sand was  placed
 over the  finished  liner.  No traffic was  allowed on  the completed  area  before
 refuse was  spread  over  the  liner  from the top.

      QA testing  of the  constructed  liner  indicated that  the  bentonite content
 ranged  from  8.5  to 15 percent by weight and  averaged  about 11.2  percent by
 weight.   Greater than 90  percent  compaction  was  achieved  in all areas with
 variations from  93 to 100+ percent  standard  Proctor density.  The moisture
 content varied from 3 to  12  percent.

     7.2.15.6.3  Monitoring Systems—Methods used to  install the various
 monitoring systems were not available.

 7.2.15.7  Performance—                              -
     Analysis of water samples collected from lysimeter 1, surface-water
 monitoring points, and groundwater monitoring wells indicates that leachate
 has passed through the liner and entered the groundwater.  Liquids have also
 been detected but not analyzed in lysimeter 2.  Table 7-9 contains the
 results of the analysis for biochemical oxygen demand (BOD), COD, total
 coliform, and fecal coliform at several of the monitoring points.

 7.2.16  Site 0

 7.2.16.1  Physical  Description—
     This landfill  is approximately 2 acres in size.  It is lined with a
mixture of local  soil combined with a 1:1 mix of bentonite and lime.  The
 ime was added to reduce the swelling potential of the bentonite.  A
 leachate collection system is on top of the clay liner.  Several groundwater
                                    7-59

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        TABLE 7-9.  WATER SAMPLE ANALYSES:   BOD,  COD,  TOTAL  COLIFORM,
                             AND FECAL COLIFORM
Sampling location
(see Figure 7-20)
L ia
SW lb
SW 2b
SW 3b
SW 4b
MW lb
MW 2b
MW 3b
MW 4b
BOD
(mg/L)
336
<1
<1
1
260
>800
16
13
2
COD
(mg/L)
1,560
3.9
5.8
19
400
1,870
45
100
10
Total col i form
per 100 mL
14,000
500
1,900
500
0
0
190
0
0
Fecal coli form
per 100 mL
14,000
140
320
90
0
0
0
0
0
aSample date - 12/5/83.
bSample date - 10/11/83.
                                    7-60

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 monitoring wells are located adjacent to the landfill.   The  landfill  has  been
 capped and covered with asphalt pavement.
      The leachate collection system consists of  a  stone-packed  sump  (drywell)
 with a casing pipe extending to the surface  that is  used  for observation  and
 leachate withdrawal.
 7.2.16.2  Startup Date--
      Construction of this  facility  began in  June of  1980.  It was filled  and
 capped by September  1980.
 7.2.16.3  Local  Geology and  Hydrology—
      This facility is  located  in the  southeastern United States.  Average
 annual  precipitation at the  facility  is approximately 50 inches.
      The soil  in  the vicinity  of the  landfill is composed of a mixture of
 clay,  silt, and  sand.   Soil  borings of the site  indicate that this soil
 mixture  extends  to a minimum of 10  feet.  Analysis of the native soil gave
 the  following  results:
      «   Average  permeability                    8.7 x 10-5 cm/s
      »   Plasticity index                         7.1%
      «   Liquid limit                            27.1%
      »   Plastic  limit                            20.0%
      •   Amount passing  No. 200 sieve             31.3%.
      Monitoring wells have indicated that groundwater is well  below the
 bottom of the site and  poses no potential problem.   Water samples from the
monitoring wells are taken monthly and analyzed  for PCB's, pH,  specific
 conductance, and chlorinated organics.
7.2.16.4  Waste Type—
     The major material disposed at this site was PCB's.  The facility also
contains solvents, waxes, and oils, all of which  were solidified with sawdust
prior to their disposal.
7.2.16.5  Liner Description—
     The 4-foot-thick liner consists of a homogeneous mixture  of 3  percent
bentonite, 3 percent lime,  and 94 percent native  soil.
     The physical properties  of the liner material  are:
     •  Liquid limit                            27.8%
     •  Plastic limit                          20.7%
     •  Plasticity index                       7.1%
     •  Permeability                            8.3 x  1Q-8 cm/s
     •  Amount  passing  No.  200  sieve           35.4.
                                    7-61

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     The leachate collection system consists of a stone-packed sump  (drywell)
with a casing pipe extending to the surface that is used for observation  and
leachate withdrawal.

7.2.16.6  Liner Installation—
     The liner at this facility was installed in 8-inch lifts and compacted
to at least 95 percent of maximum Proctor density.  The bottom of the  facil-
ity slopes at a rate of 2 percent to the leachate collection system.   The
sidewall slopes are 3:1 maximum.  The 3-foot-thick cap constructed of  the
same mixture was compacted to 90 percent of maximum density.  No information
on the Installation of the asphalt cover was available.

7.2.16.7  Performance--
     Due to a poor seal around the leachate collection system casing pipe
(standpipe), surface water eroded through this area and was collected  in  the
sump.  This problem was solved by removing a 12-foot-diameter section  of  the
cap surrounding the pipe.  The area was then filled with tightly compacted
pure bentonite.  A concrete dome was placed on top of the bentonite  to direct
the flow of water away from the casing pipe.  Because additional liquids  were
still being collected in the collection system, the entire cap was paved  with
asphalt.  No information was available on the performance of the facility
after the asphalt was installed.

7.2.17  Site P

7.2.17.1  Physical Description—
     The facility consists of one double-lined hazardous waste cell.   The
bottom liner is composed of leachate collection and detection systems  as  well
as a series of natural soil and bentonite/soil liners.  The side liner and
dike-containment system include a soil and a bentonite/soil liner (see
Figures 7-22 and 7-23).

7.2.17.2  Startup Date--
     The facility was constructed and began accepting waste in 1980.

7.2.17.3  Local Geology and Hydrology—
     This facility is located 1n the southeastern United States.  The  average
annual precipitation in the vicinity of this facility is approximately
52 Inches.  No information on the local geology was available.

     Groundwater at this site occurs in soil and fractured rock.  The  maximum
groundwater table 1s located approximately 14 to 15 feet below the liner
bottom.  Groundwater levels at the site fluctuate with precipitation,  tending
to be high 1n winter and spring and low in the remainder of the year.

7.2.17.4  Waste Type-
     Approximately 80 percent of the disposed waste 1s brine purification
mud.  This material has the consistency and appearance of fine, wet  sand.
The remaining 20 percent of the wastes are all mercury-contaminated
substances including sulfide treatment filter cake, retort ash,
Reductone®  filters, decomposer packing, and contaminated earth.
                                    7-62

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0>
CO
                                                     Side Liner System
                                                     (see Figure 7-23
                                                     for details)
                                                                            Waste
                                                         6ft
                                                                   Bottom Liner System
                                                                 (see Figure 7-23 for details)
                                                                                                                       Dike
                                                  \\   //    \\   //    \\   //    \\   //   \\   //   \\
                                                                                                                            \\    //   \\
                                                                        Native Soil
                                          Figure 7-22. Cross section of site P showing relationship of liner and dikes.

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VI

CO
6-in Bentonite/Soil Liner

   18 in Recompacted Clay Liner


        1-ft Drainage Layer
                      6ft
                   '•:*V"V-&^'->V^                                Leachate
                   ?&:i<&::-£+x£&t&?}:^i%X&&}^  Collection La
                                                                                                          Collection Layer

                                                                                                          -3-ft Recompacted
                                                                                                          Clay Liner
                                                         /XHf»-1-ft Bentonite/Soil Liner
                                                              •1-ft Recompacted Clay Liner
                                                                 t Leak Detection Layer
                                                               5 in Bentonite/Soil Liner
                                                              • 5-ft Recompacted
                                                              Clay Liner
\\
\\
                                                                                       \\
                                                      \\
       Figure 7-23. Detailed cross section of site P liner.

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 7.2.17.5  Liner Description—
      The liner at this  facility  is  composed of two sections:  a bottom liner
 and a side (dike) liner.   Each of these  sections has its own specifications.

      The bottom liner extends over  the entire bottom and 6 feet up the
 sides.   It is  a layered system containing two drainage or collection layers
 and two  soil liners.  From the top  layer downward, the bottom liner
 components are as follows:

      •   Leachate  collection system— 1 foot of No. 78 gravel  and sand with
         4-inch perforated  PVC pipes.

      •   Upper  soil barrier— 5 feet of compacted soil  further subdivided into
         three  layers:

         -   3 feet  of compacted native soil; permeability =
            1 x 10~4 cm/s.

         -   1 foot  of enhanced soil,  i.e., native soil  blended with 9 to
            12  percent polymer-treated bentonite;  permeability on the
            order  of 5 x 10~8 cm/s.

         -   1 foot  of compacted native soil; permeability =
            1 x  10-4
     •  Leak detection layer.  A 1-foot sand/gravel  layer with perforated
        pipe, to detect leaks and/or to control  seepage through the upper
        barrier.  The pipes are connected to several  independent monitoring
        stations to allow the determination of the approximate location of
        any leaking that might occur.

     »  Lower soil barrier.  A 6-inch layer of enhanced soil,  i.e., native
        soil blended with 9 to 12 percent polymer-treated bentonite;
        permeability on the order of 5 x ICT8 cm/s.

     o  Buffer zone.  5 feet of either in situ or recompacted  native
        soil.  Permeability = 1 x KT4 cm/s.

     The side liner system extends from a point  6 feet  above the cell  bottom
to the top of the cell.  This section will  not have  liquid impounded against;
it; therefore, the liner system is not as extensive  as  the bottom liner.
From the top layer downward, the side liner components  are as  follows:

     «  1 foot of No.  78 gravel

     •  18 inches of compacted native soil;  Permeability  = 1 x  lO"4 cm/s

     t  6 inches  of enhanced soil,  i.e.,  native  soil blended with 9 to
        12 percent polymer-treated  bentonite.
                                   7-65

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      Liner-waste  compatability  tests were  conducted from June through
 December 1980 with  a  percolation  column.   In  it was placed a compacted blend
 of 1,600 g  native soil  and  360  g  bentonite (i.e., 18.4 percent bentonite).
 The column  was  filled with  actual  facility liquids, with analysis as follows:

      •   1.87 ppm  mercury

      •   154,036 ppm chlorides

      t   pH  6.1.

      Short-term permeability results are as follows:

                Date                    Permeability (cm/s)*

                6-2-80         -             2.23 x 10~7

                6-10-80                       2.92 x ID'7

                6-17-80                       3.71 x 10-7

                7-2-80                        4.05 x 10-7

                7-18-80                       4.81 x 10-7

                7-24-80                       5.88 x 1Q-7

                Ca.  12-80                     Approximately 0

7.2.17.6  Liner System  Installation—
     The  construction methods used are as  follows:

     •  Soil spreading.  All soils and gravel were placed with scrapers
        and spread  with bulldozers.

     •  Soil compaction.  All soils were compacted to 95 percent standard
        Proctor density.  This was done by repeated front-end loader or
        scraper passes  (rubber-tired).  An independent soils laboratory
        took samples  as the work progressed, and any fill not meeting the
        minimum 95  percent  compaction was  upgraded accordingly.

     •  Mixing  of soils and bentonite.  The bottom 6-inch layer of
         "enhanced"  soil was constructed by first spreading two lifts of
        approximately 4.5 to 5  inches of loose native soil.  Likewise,  the
        top 12-inch layer of "enhanced" soil was constructed by first
        spreading four  such lifts.  Scrapers were used to spread the
        soil.   After placement of loose soil for each layer, the bentonite
        product was hand-placed at an application rate of 50
        lb/40 ft2.
     ^Calculated values based on leachate absorbed into test specimen.  All
data supplied by American Colloid Company.
                                    7-66

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         Mixing was accomplished with  a  rotiyator  until  the  color of the
         bentojiite became unnoticeable.

      t  "Enhanced" soil  compaction was  done  by  repeated passes of a
         front-end loader or rubber-tired  scraper  until a minimum of
         95 percent Proctor was  achieved.

      •  Quality assurance.  Soil  layers were sampled as the work progres-
         sed to ensure  95 percent standard Proctor density.  During con-
         struction of the "enhanced" soil  layers,  a minimum of one
         field  density  test was  performed  per 2,500 ft2 of lift.  Tests
         for moisture,  permeability, grain-size  distribution, and liquid
         and plastic limits were also  performed  by qualified soils
         personnel  on an  "as-needed" basis.

      Results from the  quality assurance of the  constructed liner indicate
 that  the wet unit weight ranged from  101  lb/ft3 to 115 lb/ft3, the
 moisture content  ranged  from 23 to 28 percent, and the laboratory
 permeability ranged from 2 x 108  cm/s to  7 x  108  cm/s.

 7.2.17.7  Performance—
      Leachate  collected  in  the  leachate collection layer was analyzed and
 found  to contain  high  levels of chlorides and measurable levels of mercury.
 Small  amounts  of  liquid  have also been  collected  from the leak detection
 system.  This  liquid does  not contain high levels of either chlorides or
 mercury.   The  monitoring wells  have not shown any significant changes.

     The performance of  this facility is very difficult to determine at this
 time.  A complete  analysis of the liquid collected 1n the leak detection
 system is  being performed.  Attempts are being made to correlate these
 results with changes in  precipitation, waste type, and water table level.
 The complete analysis was  not available at the time of this writing.

 7.2.18  Site Q

 7.2.18.1   Physical  Description—
     The landfill  consists of a single containment cell  covering an area of
 approximately  3 acres.   It is located in a former sand and gravel  pit.  The
 facility has a double liner consisting of two 4-inch tentonite/soil  layers.
 These  layers are separated by a leak detection system.

 7.2.18.2   Startup  Date—
     This  facility was placed in operation in October 1976.

 7.2.18.3   Local Geology and Hydrology—
     This  facility  is located in the northeastern United States.   Average
 annual precipitation at this facility is approximately 35 inches.

     The immediate area around the facility is mostly sand and gravel.  The
 facility 1s  located above the 100-year flood plain.

7.2.18.4  Waste Type—
     The sludge deposited in the landfill  is a black,  semisolid,  relatively
odorless material, which will support  the  weight of  small  grading  equipment.
                                    7-67

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 The sludge 1s  nonvolatile  and  noncombustlble.   It consists primarily of metal
 hydroxides and waste pigments.  Typical  sludge  composition 1s as follows:

                         Metal               Percentage

                         Iron                10  - 24

                         Lead                 5-20

                         Chromium            6-12

                         Barium              2-12

                         Calcium              4-48

                         Aluminum            1-3

                         Copper              1-2

                         Cadmium              1-2

                         Zinc                 0-1

                         Carbon              2-10

 7.2.18.5   Liner Description—
     The  cell  has a  double liner consisting of  two 4-inch layers of a
 bentonlte/soil  mixture on  the  bottom and side slopes up to a vertical eleva-
 tion of 20 feet above the  cell bottom.  The bentonite/soil layers are
 separated  by a  12-inch layer of  sand on the bottom of the cell and a 6-inch
 layer of  sand  on the side  slopes.  The side slopes above the 20-foot vertical
 level are  covered with a single  6-inch layer of the bentonite/soil  mixture.
 All bottom and  side  slope  bentonite/soil surfaces are covered with a 12-inch
 protective layer of  gravel.  The slope of the cell sidewalls varies from
 2.5:1 to 3:1.   A typical cross section of this facility is illustrated in
 Figure 7-24.

 7.2.18.6   Liner  System Installation--
     Most  of the bentonite/soil mixture used for the liner was premlxed in a
 pug mill to predetermined  proportions by closely controlling the feed rate of
 each material.   Soil was fed from a hopper onto a conveyer belt at  a constant
 rate.  Dry bentonite was fed from a hopper onto the conveyor belt on top of
 the son through a variable-rate vibratory feeder.  The feed rate of the
 bentonite was periodically checked and adjusted as necessary by weighing
 timed samples.  The  two materials were discharged into the pug mill  where
water was  added  at a controlled  rate to produce a thoroughly mixed  product at
 desired moisture content (specific value unknown).  The mixture was dis-
 charged from the pug mill  into dump trucks and was placed 1n position at a
 predetermined thickness with a grader, screened boards, and hand labor.  The
mixture was then compacted to the specifications with a backhoe-mounted
 hydraulic  tamper.

     During all  construction phases, CQA and CQC required full-time supervi-
 sion by qualified personnel and a soils consultant as required.
                                    7-68

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o>
ID
                 12-in Gravel Layer (Leachate Collection)
                                                                                                                            6-in Bentonite/
                                                                                                                            Soil Layer
                    12-in Sand Layer (Leak Detection)
                  O            O             O
                                  6-in Sand Layer
                     4-in Perforated
                     Pipes
4-in Bentonite/
Soil Layers
                                                           Figure 7-24. Cross section of site Q liner.

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7.2.18.7  Performance—
     This facility is presently active and uncapped.  As a result,  a great
deal of leachate is being collected.  Liquid has also been collected in the
leak detection system.  Analysis of this liquid shows that it has slightly
elevated levels of cadmium, lead, zinc, iron, copper, cyanide, and  COD.  The
permeability of the upper bentonite/soil liner has been determined  from the
volume of liquid pumped from the sump, the waste head, and the facility
area.  This value, as reported by the site owner, varies from
3 x 10"8 cm/s to 6.5 x 10~8 cm/s.

     Analysis of the groundwater from the facility monitoring wells has shown
no significant changes since construction of the facility and is well  within
drinking water standards.

7.3  LINER TYPES

     The feasibility of using a clay liner at a waste disposal facility
depends on several factors, the most important being availability of suitable
liner material.  The location of a facility in a deposit of low-permeability
soil lowers the facility cost by greatly reducing or eliminating liner
material transportation costs.  The cost incurred by transporting suitable
borrow soils a short distance (e.g., 5 miles or less) may allow this to be a
viable liner option.  Another type of soil liner consists of a relatively
high-permeability soil that has been augmented with certain natural or
treated bentonlte additives.  The addition of bentonite to a highly permeable
material greatly reduces the material's permeability.  These three types of
facilities (I.e., unlined, recompacted soil lined, and bentonite/soil  lined)
were included in this study.

     Two of the four unlined facilities discussed have had groundwater con-
tamination problems.  One facility had a problem due to a faulty well  instal-
lation.  No other problems have been reported at this facility.  The fourth
unlined facility has had contamination detected in one of its monitoring
wells.  A study of this contamination indicated that its source was an
adjacent drum disposal facility.

     Nine facilities with recompacted soil liners are discussed in this
chapter.  Three of these nine facilities have had some type of performance
problem.  These three facilities all have leak detection systems that were
responsible for quickly detecting and providing the Information necessary for
determining the cause of the failures.

     Four facilities with admixed (bentonite/soil) liners are discussed in
this chapter.  Two of these facilities have had small amounts of liquid
detected 1n between their double liners.  However, overall they appear to be
functioning according to their design specifications.  One facility had a cap
problem that was rapidly detected and corrected.  The liner at this facility
has had no detected problems.  The final facility with a bentonite/soil liner
that 1s discussed in this section has had performance problems.  Leachate has
migrated through the 4-inch liner and has resulted in extensive groundwater
contamination.
                                    7-70

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 7.3.1  Unlined Facilities      ( .,* •        ^  ,

      Although~the purpose of this document is to discuss  clay liners,  in  some
 cases information relating to waste disposal  and clay liners  may be  obtained
 from the case histories of unlined disposal  sites.   Generally speaking,
 unlined sites are located in soil formations  that are relatively low in
 permeability.  However, such soil formations  are rarely homogeneous.  They
 generally contain sand or gravel seams,  varying  amounts of  organic matter,
 and cracks or fissures.  In some cases,  they  may also contain lenses of
 gypsum, limestone,  or other soluble material. Discontinuities such  as these
 are often excavated and then backfilled  with  recompacted  clay prior  to waste
 disposal.  When this is not specified or when highly permeable areas are
 unnoticed during facility construction,  the siting  of an  unlined hazardous
 waste disposal  facility in a heterogeneous soil  may cause severe performance
 problems.

      (Examples of unlined waste disposal  facilities  are sites  A,  B, C,  and G,,
 These four facilities are 8 to 30 years  old.   Extensive groundwater  contami-
 nation has occurred at two of these facilities:   a  slight problem due  to poor
 well  installation procedures occurred at one  facility, and  contamination  in a
 well  at the fourth  facility is thought to have come from  an adjacent
 abandoned drum disposal  operation.

      Facility B, a  zone-of-saturation or intergradient landfill,  has had
 severe groundwater  contamination problems. This facility is  located in a
 low-permeability glacial  till  deposit.  Lenses of sand or gravel  that  were
 encountered during  the site construction were excavated and backfilled with a
 minimum of 5 feet of recompacted clay.  A buildup of leachate in  the landfill
 due to the disposal  of unsolidified liquids,  precipitation, and  seepage
 caused waste to enter a permeable deposit that had  been improperly sealed
 with  clay.  This resulted in leachate migration  and groundwater
 contamination.

      Facility C is  also  unlined.  Geological  investigations revealed that
 calcium carbonate seams  and nodules were present throughout the entire area.
 The design specifications called  for  the excavations  of such  seams and then
 required  the excavated areas  to  be  backfilled  with  the  local  clay-shale
 soil.   Groundwater  contamination  at this facility can  be attributed  to
 inadequate excavation  of  the  calcium  carbonate deposits,  inadequate  recompac-
 tion  of the  excavated  areas,  or  lack  of  sufficient waste/liner material
 compatibility testing.

      Initial  groundwater  samples  taken from a monitoring well  at site A had
 pH  values  between 10.7 and  11.3.  An  investigation  into the problem revealed
 that waste migration from the unlined  facility was not the cause.  Instead,
 the contamination was  traced to some  steel-mill slag that was  used as well
packing instead of the specified clean gravel.  This problem was remedied,
and since  that time no other problems  have been reported.

     Facility G is an old, unlined hazardous waste disposal  facility.
Samples from a groundwater monitoring  well at this facility  have contained
high levels of various pollutants.  A  study of this  contamination indicated
that its source was an old drum disposal  site  (previously  owned by another
company) located adjacent to the landfill.  This  drum disposal site  is
                                    7-71

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located on a sand and gravel seam.  This permeable seam was determined to be
the mechanism by which the contaminants were transported to the monitoring
well at SiteTS.

7.3.2  Recompacted Soil Liners

     Recompacted soil liners are the most common type of soil  liner in
current use.  This category consists of both recompacted in situ soil  liners
and liners constructed of material that has been transported to the facility
from a nearby borrow area.  Sites D, E, F, H, I, J, K, L, and  M are all  in
this category.  Some of these facilities have a double liner system (in  the
case of sites D and F, one of the liners is a synthetic).  When this is  the
case, the drainage layer separating the clay liners is called  a leak detec-
tion layer or system.  All of these facilities have either a leachate collec-
tion or a leak detection system (in some cases, both).  These  facilities are
4 to 9 years old.  The performance at these facilities is quite varied.   Six
of the facilities (sites D, E, F, H, K, and M) appear to be functioning  as
planned with only a few minor problems.  In the case of site K, the liquid
volumes removed from the detection system were used to calculate the liner
permeability.  The calculated values were all lower than the design
specifications required.

     The remaining three facilities (sites I, J, and L) have all had
performance problems.  For example, the clay liner for a pond  at site I  was
left empty and unprotected for several months.  During this time desiccation
cracks formed in the liner.  Failure to repair the liner prior to waste
placement resulted 1n waste migration into the leak detection  layer.  Waste
migration into the leak detection system also occurred at site L shortly
after waste placement.  An investigation was unsuccessful in determining the
location of the leak.  However, it was determined that the lower compacted
clay liner was not leaking.  The other recompacted clay-lined facility with
performance problems, site J, also has a leak detection system.  In this
case, perchloroethylene was mistakenly placed into a pond.  Approximately 6
to 9 months later, and literally overnight, the "perc" penetrated the liner
and was detected in the leak detection system.  The apparent incompatibility
of the "perc" and the liner material is consistent with current research on
the effect of chlorinated solvents on clays.

7.3.3  Admixed Liners                                -

     Admixed liners are those composed of permeable soil and an additive
designed to decrease its permeability.  Commonly used additives include,
asphalt, fly ash, soil cement, and polymer-treated or natural  bentonite.
Bentonlte, a natural clay mineral, is the only additive discussed in this
document.

     The addition of bentonite (generally 3 to 15 percent is used) to a
highly permeable soil can decrease its permeability so that 1t can be used
as a Uner material.  A discussion of the physical and chemical properties of
bentonite as well as its advantages and disadvantages as a liner material  may
be found 1n Chapters 2 and 5 of this document.

     Facilities N, 0, P, and Q are all  lined with bentonite/soil admixtures.
These facilities are 5 to 11 years old.  The liner configurations at these
                                    7-72

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 facilities are quite varied.  Site'O has a 4-foot-thick  native  soil  liner
 containing 3 percent bentonite and 3 percent lime.   The  lime was  added  to
 reduce the swelling potential  of the bentonite.   Sites P and Q  are  lined with
 a layered system containing bentonite/soil  liners ranging from  4  to  12  inches
 thick and leak detection systems.  Site P has the additional protection of a
 series of compacted native soil  liners.  Facility N  is lined with a  4-inch
 bentonite/sand liner.  Two lysimeters and a groundwater  pumping system are
 located below the liner, and a leachate collection system is on top  of the
 liner.

      Just as the liner systems at these four facilities  are varied,  so are
 their performances.  Both sites  P and Q have had  small amounts of liquid
 detected in  their leak detection layers;  however, overall  they seem  to be
 functioning  according to specifications.   In the  case of  site Q, the liquid
 volumes collected were used to calculate  the as-built liner permeabil-
 ity.   This value ranged from 3 x 10"8 cm/s  to 6.5 x  l(r8  cm/s, which is
 less  than the  specifications required.  The  source and quality of the liquid
 being collected  from the detection  system at site P are currently being
 investigated by  the site owner.

      Site 0  had  a problem with liquid eroding the cap and  infiltrating
 through the  eroded section.  This problem was corrected by repairing the
 eroded portion and then paving the  entire cap with asphalt.  The liner at
 this  facility  has not had any  detectable  problems.

      Finally,  facility N,  a  very large municipal waste disposal  facility
 located in an  abandoned sand and gravel pit,  has produced extensive contami-
 nation that  has  been  detected  in  the  subsurface monitoring layer,  the
 lysimeters,  and  several  groundwater monitoring wells.  Analysis of the con-
 tamination indicates  that the  leachate  is passing through the 4-inch liner
 and entering the groundwater.

 7.4   SITE CHARACTERIZATION

      The  location  of  a clay-lined hazardous waste disposal facility may have
 a significant  effect  on  its  performance.  The site-specific geology, hydrol-
 ogy,  and  climate must.be  evaluated thoroughly prior to the facility design
 and construction.   Some  of the geological factors that must be investigated
 include the  local  soil  type, permeability, and nature*of the soil  deposit
 (e.g., whether it  contains  continuous or discontinuous sand or gravel seams,,
 gypsum, or other reactive  material seams and the depth of the deposits).

      Hydrological  factors  that must be investigated include location of the
 water  table, location  of  any perched water tables above the main water
 table„ and the groundwater and surface-water flow patterns.  Problems
 associated with  high water tables include excessive pressure on  the side or
 bottom  liners.   This  hydraulic pressure may cause sidewall slumping or
 collapse or  bottom  heaving.  High water tables may also result  in  the
 unwanted  infiltration  of groundwater.  For a facility under construction,
 this may make compaction and other liner installation procedures difficult  or
 impossible without continuous groundwater pumping.  For a closed facility,
groundwater  infiltration may result in overloading the leachate  collection
system, causing high leachate levels in the facility.
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     Site-specific climate data such as average temperature and amount of
prec1pitation_also must be known.  Locations that have below-freezing temper-
atures  for  long periods of time have the potential for freeze/thaw cycling of
unprotected liners.  This may  result in increased liner permeability and poor
liner performance.  Hot climates, on the other hand, may affect clay liners
by  causing  excessive evaporation and possibly desiccation of the liner.  Clay
liners  located in hot, arid climates are even more susceptible to desiccation
and cracking.  On the other hand, excessive precipitation at an open clay-
lined facility may cause a buildup of hydraulic head on the liner, thus
increasing  the flow of liquid  through it.  Excessive precipitation may also
cause a rise in the groundwater table and the previously discussed problems
associated  with this phenomenon.

     A  complete discussion of  these site-specific factors, their associated
problems, and the potential failure mechanisms involved may be found in the
preceding chapters of this document.

7.4.1   Case Studies

     Several performance problems or liner failures that may have been
partially caused by inadequate site characterization are illustrated by case
studies  B,  G, and I.

     Site B, a zone-of-saturation or intergradient facility, is located in a
low-permeability soil formation.  Sand or gravel  seams that were encountered
during  excavation were to be removed and replaced with recompacted clay.  No
additional  recompaction was specified.  A buildup of leachate within the
Hner due to precipitation, the disposal of free liquids, and seepage caused
the gradient to reverse.  Within the site, apparently a sand seam was either
not discovered or not properly sealed during construction.  The leachate
flowed  through this sand seam and caused severe groundwater contamination in
a limited area of the property.

     Another problem caused by a sand seam was discovered at site G.  Contam-
ination  in  one of the facility monitoring wells was initially attributed to
waste migration from within the site.  However, an investigation Into the
problem  revealed that the source of contamination was an adjacent abandoned
drum disposal facility.  Leachate from this facility entered a water-bearing
sand seam that encountered one of the wells at site G*.

     Site I  is located in a semiarid climate.  Three ponds with double clay
liners were  installed in the fall of 1980.  Two of the ponds were filled
shortly  after construction, while the third pond was not filled until the
following spring.  During this time, the unprotected clay Hner developed
severe desiccation cracks.  These were not repaired prior to filling; con-
sequently,  contaminated liquid passed through the liner and began accumulat-
ing in  the  leak detection system.  This problem,  which was caused by the arid
climate  and  the loss of water from the liner, could have been avoided with
adequate liner maintenance and a rigorous preservice inspection.

7.5  INSTALLATION OF CLAY LINERS

     This section presents a very brief discussion of clay Hner installation
methodology and procedures.  Only one case study 1s Included for discussion
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 because 1t is very difficult to attribute a liner failure  to  poor  construc-
 tion techniques.  For a complete discussion of this  topic,  see  Chapter  5.

 7.5.1  Installation Methods

      It is widely believed that the performance of clay  liners  is  affected by
 the equipment and procedures used to install  them.  Conclusive  field data to
 support this belief, however,  are not available.   Specific  items that need to
 be controlled during clay liner construction  are  discussed  in the  following
 sections.

 7.5.1.1  Excavating, Grading,  and Foundation  Preparation--
      The excavation and grading of the bottom and side slopes of the liner
 foundation should be conducted according  to design specifications.  This
 generally  requires the use of  construction equipment such as  dozers,
 backhoes,  scrapers, and graders.  For unlined facilities constructed in low--
 permeability soil, special  care must be taken to  locate and fully  excavate
 all  permeable zones that may allow for leachate migration.  For facilities
 that are to be lined with recompacted local soil  or  admixed materials,
 suitable liner materials are generally excavated,  stockpiled, and  used as
 required.   In all  cases, the specified slopes and elevations  of sidewalls and
 bottoms as well  as those of collection system pipes  and manholes must be
 carefully  controlled.  This will  help ensure  that the liner is  properly
 located regarding the water table and local geological features.   Specified
 side and bottom slopes are  also necessary so  that leachate will flow to the
 collection system pipes and sump,  thus preventing  the "bathtub" effect.

 7.5.1.2 Liner Materials--
      Native soil  liner material  may be excavated  from the site  during
 foundation preparation or may  be brought  to the site from a nearby borrow
 area.   Admixture  materials  may be  shipped  to  the  facility in bags or bulk
 form.   In  all  cases,  the use of materials  that are specified  in the facility
 design  is  extremely important.   As  previously discussed, materials such as
 sand, rocks,  roots,  or other organic  matter,  if included in the liner,  will
 greatly affect  its  permeability and  ultimate performance.  When materials
 such as bentonite  are  to be added to  in situ materials to form a liner,  the
 bentonite  content must be carefully  controlled.  The use of inadequate
 quantities  of bentonite  will produce  a  liner with higher than required
 permeability and  lower than specified performance.

 7.5.1.3  Moisture Content/Density/Compactive Effort--
     The relationship  among moisture  content,  density, and  compactive effort
 is discussed in Chapter  2.  Careful control of these  parameters  is  necessary
 throughout all phases  of  liner construction.  The final  liner permeability
 and performance depend on proper moisture  control  and distribution, mixing,
 and compaction techniques.  Too little or  too much water added to  the liner
material will make it difficult to compact to the specified density, thus
 affecting permeability.  Inadequate mixing of materials  may result  in a
 heterogeneous liner.   Insufficient compactive effort  may result  in  a liner
 that is more permeable than required.
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 7.5.2  Quality Assurance/Quality Control For Clay Liners

      A survey of  hazardous waste surface impoundment technology has found
 that  rigorous  quality  assurance is necessary to achieve good site performance
 (Ghassemi  et al.,  1984).  Liner failures at several impoundments included in
 the survey were attributed to various factors including "failure to execute
 proper quality assurance and control."  The success of surveyed facilities
 that  have  performed very well is attributed to many factors including "the
 use of competent  design, construction and inspection contractors, close
 scrutiny of all phases of design, construction and QA inspection by the
 owner/operator, excellent CQA/CQC and recordkeeping during all phases of the
 project, and good  communications between all parties involved in establishing
 the sites."

      Specific  problems that may result in clay liner failure and that can be
 avoided with careful CQA include:

      •  Use of materials with specifications other than the ones in the
        approved design

      •  Lack of careful screening and testing of incoming materials to remove
        roots and  other organic matter, rocks, pockets of permeable
        materials, and other foreign objects prior to placement

      •  Lack of adequate moisture control both prior to and after compaction

      •  Improper size  reduction, mixing, and spreading of Uner materials

      t  Use of  inadequate liner materials (especially important with
        bentonlte/soil liners)

      t  Failure to follow installation procedures specified in the design

      t  Use of  improper construction equipment

      •  Application or specification of inadequate compactive effort.

      The following case study is of a surface impoundment that has had
 performance problems.  Due to insufficient information, this case study is
 not Included In Section 7.2.  The problems at this facility may have resulted
 from  a combination of factors, one being the lack of adequate CQA.

      A sewage-treatment lagoon was to be lined with 3.7 pounds of
 polymer-treated bentonite per square foot of liner mixed with the native soil
 to a  depth of 4, inches.  The particle size of the bentonite that was supplied
 did not meet the original specifications, making it very difficult to spread
 and mix the material adequately.  Problems were also encountered in achieving
 proper moisture content.  After the bentonite/soil  layer was compacted, the
 final  permeability of the liner was to be determined by filling the lagoon
with water to a depth of 15 feet.  The decrease in .liquid head and the
 evaporation rate were then to be used to determine the as-built liner
 permeability.  Unfortunately, the as-built liner permeability was much
greater than expected.  Actual  as-built permeabilities were never determined,
however, because the water flowed through the Uner faster than it could be
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 pumped  Into  the  lagoon.   Examinations of  the  liner profile revealed large
 discontinuities  in  the  liner materials, which explains the high
 permeability.                   -   v-        ^

      A  second  attempt to  construct  the liner  to the same specifications was
 successful.  All  phases of  liner  installation (by a different contractor)
 were  carefully monitored  by the site owner.   Final permeability testing con-
 firmed  that  the  liner exceeded the  required specifications.  A cross section
 of this liner  revealed  uniform thickness  and material content.

      A  complete  discussion  of CQA/CQC may be  found in Chapter 5 of this
 document.

 7.6  WASTE TYPES

      Prior to  recent Federal regulations  (Federal Register, 1982), unsolidi-
 fied  liquid  wastes  either containerized or in bulk form were often disposed
 of in landfills.  Since these recent regulations, free-standing liquid wastes
 are required to  be  removed  from drums and solidified prior to final dis-
 posal.   While  the option  still exists to  store liquids in surface impound-
 ments or evaporation ponds, free  liquids  must be removed prior to final
 facility closure.

 7.6.1  Free  Liquids

      Many performance problems have resulted from the practice of placing
 containerized  or  bulk free  liquids  in waste disposal facilities.  With bulk
 liquids, a liquid head is imposed on the  liner.  If the head becomes too
 great or if  the waste material is incompatible with the liner material, the
 waste has a  much  greater  chance of  infiltrating into or through the liner.

      Fifty-five-gallon drums, which are often used to contain free liquids,
 have  the potential to degrade with time.  This can result in leaky drums,
 which,  in turn, may cause leachate levels to build and the performance
 problems associated with  this phenomenon  to occur.  Several  problems are also
 associated with the waste placement and closure operations of a facility that
 contains drums.   Drums are usually stacked upright 1n several  layers or
 lifts.  Absorptive material  such as soil   is then placed between the drums and
 compacted to fill all  voids.  It is difficult to determine when all  of the
 lower voids are filled and when the material  has been compacted properly.  If
 the spaces are not completely filled,  piping Into the spaces  between the
 drums may occur.  This can result in differential  settlement  and cap failure,
which may lead to Increased liquid infiltration  and hydraulic  gradient on the
 liner, thus affecting  its performance.

     An example of a facility where a  performance problem has  resulted,  at
 least in part,  from free liquid disposal  is site B.   This facility is
approximately 13 years old.   It is a zone-of-saturation  (intergradient)
 facility where liquids were  not solidified prior to disposal.   These
unsolidlfied liquids along with the accumulated  precipitation  and  seepage
 resulted in a "bathtub"  with leachate  seeps penetrating  the  cap/liner
 interface.
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      Present landfill  regulations  require  that  leachate collection and
 removal  systems must be installed  immediately above the liner.  These systems
 must be  designed to ensure  that  the  leachate depth does not exceed 30 cm.
 Properly functioning leachate  collection systems along with the regulation
 preventing free liquids from being disposed of  in landfills should prevent
 similar  future performance  problems  from occurring.

 7.6.2 Stabilized or Solidified  Liquids

      As  previously mentioned,  Federal  regulations require that free liquids
 not  be placed in landfills.  In  response,  free  liquids are now removed,
 solidified,  or stabilized prior  to their final  disposal.  Removed liquids may
 be recycled,  impounded,  used as  fuel,  or in some way treated and then placed
 in a landfill  either in  drums  or bulk.  The solidification process may be
 accomplished  by mixing  the  liquid with absorptive material such as lime,
 cement kiln  dust,  fly ash,  or  some other substance.  Stabilization of wastes
 may  include  processes such  as  neutralizing acidic or basic wastes or
 precipitating heavy metals.  These processes generally decrease the toxic or
 hazardous  nature of the  waste  and are  currently practiced at many of the case
 study sites  in Section  7.2.

      A procedure that provides protection  from  leaking drums is practiced at
 site E.  Here, a "calculated amount" of "absorptive material" is placed
 beneath  each  lift of waste.  This material will theoretically absorb any
 liquids  that  might leak  from the drums.  The success of this method is not
 proven at  this time as  site  E  has had  large volumes of leachate accumulating
 in some  of its waste trenches.

 7.6.3 Sludges and Solid Wastes

 7.6.3.1  Sludges--
      Depending on the water  content, sludges may be either landfilled or
 placed in  evaporation ponds.   However, in  both  cases, it is important that
 most of  the moisture be  removed  prior  to final  facility closure.  Case
 studies  M, P,  and Q are  all  landfills  that contain various types of sludges.
 All  of these  facilities  contain  both leachate collection systems and some
 form of  leak  detection  system.

      Site  M uses  a special procedure for waste  placement.  This procedure
 Involves mixing  a  thin  layer (approximately 2 feet) of locally available soil
 with  a thin layer  of the inorganic lime sludge, thereby reducing the overall
 moisture content  of the  material and giving it  structural  stability.  The
 range of the  soll-to-waste ratio varies from 0.5:1 to 1.5:1.  Exact mixing
 proportions are  determined in  the field and judged sufficient when the
 landfill equipment  is able to  drive over the mixture.

     Facilities P  and Q  contain brine purification mud and metal  hydroxide
 and waste pigment  sludge, respectively.  These facilities  are both lined with
 bentonlte/soil admixtures.  The bottom and lower side liners at both of these
 facilities are thicker than the upper side liners to provide extra protection
 1n areas where a liquid  head may be present.

     The following case  study 1s not included  in Section  7.2 due  to insuf-
ficient information.  Enough information  is available,  however,  to allow a
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 a failure that occurred at this facility to be  attributed  to  improper waste
 placement procedures.  This double-lined facility was  originally  designed  for
 the disposal  of solid wastes.   A change  in  the  parent  company's waste
 disposal  needs resulted in this facility accepting  high-liquid-content
 sludges.   The sludges were transported to the site  in  tank  trucks that would
 back up to the facility and dump their load through a  pipe  whose  outlet was
 well above the base of the liner.   The impact of the sludge on the liner
 caused severe liner erosion and groundwater contamination probably as a
 result of an  erosional  breach  in the  liner.

 7.6.3.2  Solid Waste--
      Solid wastes may be landfilled in containers such as 55-gallon drums  or
 in  bulk form.  When wastes are  landfilled in drums, all free  liquids must  be
 removed or solidified prior to  final  disposal.  Care must be  exercised to
 make certain  that the voids between adjacent drums  are filled with well-
 compacted soil  or other material.   Problems  that may result from  the disposal
 of  drums  are  discussed  in  Section 7.6.1.

      Solid wastes such  as  contaminated soil  or  other fine uniform material
 may be emplaced and compacted in lifts.   When this method is  used, the void
 volume in the landfill  is  reduced;  thus,  future problems due  to settlement or
 piping are less likely  to  occur.  Solid wastes  that are not uniform, such as
 unshredded tires, scrap metal,  and  municipal solid wastes, on the  other hand,
 are more  difficult  to compact thoroughly  and therefore have the potential to
 settle differentially.   This can be minimized by crushing or  shredding the
 waste,  thereby reducing its void spaces and  overall volume.  The use of a
 landfill  compactor  will  also help to  prevent future problems due to piping
 and settling.

 7.6.4   Waste  Compatibility

 7.6.4.1   Waste/Liner Compatibility--
      Laboratory tests suggest that  dilute aqueous leachates will  not affect
 the permeability of clay liner  materials  if  the moisture at compaction is
 uniform and close to optimum and if compaction  is uniform.  However, data
 from several  studies suggest that drastic increases in permeability can
 result from certain clay-chemical interactions.  Examples of organic
 chemicals that  have been demonstrated to  increase clay soil permeability are:
 aliphatic and  aromatic  hydrocarbons (e.g.,  cyclohexarre, heptane,  kerosene,
 naphtha,  benzene, and xylene),  alcohols  (e.g., methanol and ethylene glycol),
 ketones (e.g.,  acetone  and  dioxane),  amines  (e.g., aniline and pyridine),
 carbon  tetrachloride, and  nitrobenzene.  Changes in permeability have also
 been noted  with strongly acidic permeant fluids.

     Bentonite  is sometimes given a polymer treatment to improve  its
 resistance  to  the effects  of normally incompatible fluids.  The long-term
 viability  of polymer-treated products needs to be verified.

     The  enormous variability in clay soil from different locations
 complicates the task of predicting clay-chemical compatibility.  Data from
 several laboratory  studies suggest the possibility of drastic  increases  in
permeability as a result of certain clay-chemical  interactions.  It should be
emphasized, however, that many aqueous leachates have  been tested  and
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 produced no  significant increases  in  permeability.  For a detailed discussion
 of clay-chemical  interactions,  see Chapter 4 of this document.

      Facilities  C and  0 have  both  had liner failures that have been attrib-
 uted to liner/waste incompatibility.   In  the case of site C, an investigation
 of groundwater contamination  identified the facility's treatment ponds as the
 probable source  of the pollution.   This conclusion was based on the fact that
 the materials  in  the treatment  ponds  were usually of low pH and would have
 reacted with carbonate seams  and inclusions in the surrounding soil.  Several
 of the  disposal  trenches at this facility were also used for the disposal of
 highly  acidic  waste, in this  case  oil  reprocessing sludges.  These acidic
 sludges may  have  also  reacted with the carbonate inclusions, creating paths
 for leachate seepage and groundwater  contamination.

      The Uner failure at site  J occurred almost overnight.  Samples of
 liquid  removed from the leak  detection system at one of the ponds on one day
 were reported  to  be "clean."  Samples  taken the following day contained over
 11.2 percent perchloroethylene  plus small amounts of other chlorinated and
 nonchlorinated organics.   The facility was allegedly not accepting wastes
 with more than a  trace of perchloroethylene.

      An  investigation  into the  problem revealed that aqueous wastes coming
 from one of  the disposal  facility  customers contained approximately 5 percent
 degreaslng fluid  waste that contained  perchloroethylene.  This waste was to
 have been stored  in  a  separate  tank at the originator's plant.  Evidently, it
 was  not  made clear  to  the workers where to put the "perc" waste, and it was
 placed  in an aqueous waste storage tank.  Being insoluble and heavier than
 water,  it sank to the  bottom.   When a  tank truck from the disposal  facility
 would collect  a load of aqueous waste, it would also receive a few hundred
 gallons  of the "perc"  waste.  The waste sampling method used by the disposal
 facility on all loads  of  incoming waste was not able to sample the bottom few
 inches of each load.   In addition,  the parking area where all  incoming
 truckloads of waste were sampled was slightly sloped,  causing the relatively
 small amount of "perc" waste  in the bottom of the tanker to flow to the back
 of the truck where  it  could not be reached by the sampling device.

     Over a period of  approximately 9 months,  the aqueous waste containing
 "perc" was placed into one of the clay-lined ponds and went unnoticed until
 the  Uner failure occurred.  The apparent incompatibility is consistent with
 current  research on the effects of chlorinated solvents on clays.

7.6.4.2  Waste/Waste Compatibility--
     Large disposal facilities  that accept most types  of wastes,  such as
 sites E and F,  generally have a waste placement plan.   Such a plan  is used to
 separate incompatible  or reactive materials and in some cases to place
 together materials that produce "favorable reactions."

     Most cells at site F are divided into five subcells.  The purpose of
these subcells  is to isolate the various waste groups  accepted'at the
facility, thereby preventing the interactions  of incompatible wastes.  The
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 waste categories, percentage of total  wastes,  and separation  rationale  at
 site F are as_follows:
                                • -  *         .«?•' •  • •
      •  General  wastes.  These wastes  represent  approximately 44  percent of
         the total waste volume accepted at  site  F.   General wastes  are
         defined  as materials of both an organic  and  inorganic nature  that do
         not contain a significant quantity  of  any of the  other waste
         categories.

              The hazardous  acidic or acid-generating materials are  covered
         with lime to ensure that  any acid that is generated will  be
         neutralized.


      •  Pseudo metals.   This type of material  represents  approximately  6
         percent  of the  total  waste volume accepted at site F.  Pseudo metals
         are arsenic, antimony,  bismuth,  and phosphorous.  Chalcogens,
         beryllium, and  any  of their compounds  as  well  as  alkaline-sensitive
         materials are also  disposed of in this subcell.

              This subcell has a pH buffer system  that maintains pH  levels
         between  6 and 8.

      •  Heavy metals.  These wastes represent  approximately 15 percent  of the
         total waste volume  accepted at site F. This group is  comprised of
         all  heavy metals  and asbestos.  This subcell  contains  the smallest
         amount of organic materials, which  helps  to  reduce fire hazards
         caused by the reaction  of strong oxidizing agents with organics.

      «  Highly flammable  wastes.  This type of material represents
         approximately 12  percent  of the  total  waste  volume accepted at  site
         F.   These materials generally  exhibit  a flash  point between 80  and
         100   F.   These  materials  are kept apart from powerful  oxidizing
         agents,  materials that  are prone to spontaneous heating, or materials
         that react with air or  moisture  to  evolve heat.

      (i  Toxic materials.  These wastes  represent approximately 23 percent of
         the  total  waste volume  accepted  at  site F.   Included in this category
         are  all  waste materials containing more than 15 percent by weight of
         highly toxic organic  compounds,  carcinogens, PCS's, and other
         halogenated  wastes.   No solvent-type wastes are permitted in this
         subcell.

7.7   PERFORMANCE MONITORING

     Several methods  can be used to monitor the performance of clay-lined
landfills.  These methods generally involve groundwater monitoring or
monitoring of the unsaturated zone directly beneath the clay liner.
Monitoring the quantity and quality of the leachate above  the liner  may  also
give some indication of the facility performance.  This type of monitoring
program for a facility should be able  to detect performance problems,  such as
leachate migration, soon after they occur.   This  will enable the  rapid
remediation of any problems  and prevent serious groundwater contamination.
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7.7.1  Unsaturated Zone Monitoring

     Two systems that are commonly used to monitor the unsaturated zone
beneath a clay liner are lysimeters and continuous-coverage leak detection
systems.  A continuous-coverage leak detection system generally consists  of  a
flexible membrane overlain by a porous layer that contains perforated
collection pipes.  Just as with a leachate collection system,  the porous
layer is usually sloped so that any detected fluid will  drain  to a sump.
Here the liquid may be sampled and analyzed for hazardous constituents.
Total liquid volumes removed from a detection layer may also be used to
estimate the liner permeability.

     The advantages of a continuous-coverage leak detection system include
its ability to provide early indications of the liner performance and  its
ability to detect and collect all  liquids that appear in the detection
system.  The disadvantages of a continuous-coverage detection  system include
its relatively high cost and the possibility that the leachate,  if a chemical
compatibility failure should occur, might spread out upon and  damage a large
portion of the lower clay liner or foundation soil.

     Another approach to unsaturated zone monitoring involves  the use  of
either pressure-vacuum lysimeters or collection lysimeters. Pressure-vacuum
lysimeters consist of a porous cup, placed in a bore hole, that a vacuum may
be applied to.  This vacuum causes pore liquids to collect in  the porous
cup.  The liquid is then removed and analyzed for hazardous constituents.  A
collection lyslmeter, on the other hand, is a lined gravel or  sand-filled
basin or trench beneath the primary liner.  A collection pipe  located  at  the
low point of the lysimeter leads to a sump from which any detected liquids
can be sampled and analyzed.

     The following discussion on the advantages and disadvantages of
collection and pressure-vacuum lysimeters is taken from Kmet and Lindorff
(1983).

     Both pressure-vacuum lysimeters and collection lysimeters can be  used to
     monitor the unsaturated zone beneath a landfill and provide an early
     Indication of landfill performance.  Each has its own advantages  and
     disadvantages.
                                                     «>
     The major advantage of a collection lysimeter is that it  provides a
     method of monitoring the quantity as well as the quality  of leakage  from
     the base of a landfill.  If one assumes that the leakage  reaching the
     lysimeter is representative of leakage over the entire base of the site,
     it is possible to calculate the volume of leakage from the entire
     landfill  and thus assess the effectiveness of the liner in attenuating
     the leachate and in limiting the rate of leachate movement.

     Also, collection lysimeters do not require the special equipment  or the
     care necessary to sample pressure-vacuum lysimeters properly. Samples
     can be taken from a manhole or riser by a bailer rather than a vacuum
     pump.  In addition, collection lysimeters do not require  that a vacuum
     be placed on the system at least several  days prior to sampling,  as is
     the case  with pressure-vacuum lysimeters.  When the monitoring results
     from a landfill  indicate that one or more pressure-vacuum lysimeters are
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      dry, one is never sure whether there was  insufficient soil moisture or
      whether jmproper sampling techniques were used.  With collection
      lysimeters, one is reasonably certain  that if  liquid is present in the
      subsurface, it will  be collected.   Collection  lysimeters also eliminate
      the problem of frozen  lines  in cold weather that can occur with
      pressure-vacuum lysimeters.

      Research,  including  work  done by Apgar and Langmuir (1971); Johnson and
      Cartwright (1980), has suggested that  some chemical constituents may be
      filtered out by the  porous membrane of the pressure-vacuum lysimeter,
      thereby producing inaccurate  water  quality data.  This is not a concern
      with collection lysimeters since no membrane is present.

      The major  disadvantage of a collection lysimeter in comparison with a
      pressure-vacuum lysimeter is  the lower cost and shorter time required
      for pressure-vacuum  lysimeter installation.  Whereas a pressure-vacuum
      lysimeter  is installed in a bored hole, construction of a collection
      lysimeter  necessitates excavation of sufficient area to appropriate
      grade  to install  the basin, collection pipe, and manhole.  A substantial
      number of  pressure-vacuum lysimeters could be installed in the time and
      for the cost of one  collection  lysimeter.  A pressure-vacuum lysimeter
      can be installed for less than  $100 plus drilling costs.  Although data
      is  [sic] limited, the  cost of collection  lysimeter installation,
      including  excavation,  materials, and construction costs, is expected to
      be  several  thousand dollars and can approach $10,000 for the larger
      lysimeters.

      Another disadvantage is that  only one collection lysimeter can be
      installed  at a  given location.  Therefore, data is [sic] generated for
      only one depth  in the  unsaturated zone, typically just below the clay
      liner.   In  contrast, pressure-vacuum lysimeters are frequently installed
      in  a nest  at different depths  to monitor changes in water quality with
      depth.

      Several  of  the  facilities discussed in Section 7.2 of this document have
 some  type of unsaturated zone  monitoring system.  Six of these
 facilities—sites  H,  L, M,  N,  P, and Q—are landfills and three—sites I,  J,
 and K—are  ponds.  Sites H  and N both have lysimeters beneath their clay
 liners.   Facility H  has two I,200-ft2 lysimeters directly beneath the
 4-foot-thick recompacted clay  liner.  An additional  lysimeter is located
 under the leachate storage  basin.  For approximately 9 months after the start
 of landfill ing operations,  small quantities of  liquid were removed from the
 lysimeters  under  the  landfill  liner.  These liquid volumes declined steadily
 over  time and were reduced  to  zero 1 year after the start of landfill
 operations.   The  liquid that was initially collected in the  lysimeters is
most  likely  soil moisture that was released after liner construction.

      Facility N also  has two lysimeters  beneath the liner.   This facility
also  has  a groundwater drain that  is used to lower the groundwater table.   An
 interesting  fact about this facility is  that although highly  contaminated
 liquids have  recently been  removed from  the  lysimeters,  'contaminated  liquids
were  first discovered in the groundwater drain  manhole.   This  has  continued
to be the location where the majority of contamination has been  detected.
                                    7-83

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      The three ponds  with  unsaturated  zone monitoring all have continuous-
 coverage leak_detection  systems  between  two  recompacted clay liners.  At two
 of the ponds,  facilities I  and J, major  performance problems have developed
 in the upper clay liners.   In both  cases, the problems were quickly detected
 (overnight  at  site J)  and  corrected, thus preventing any contamination from
 penetrating the lower liner.  The third  double-lined pond, site K, has had
 small  quantities  of liquid  accumulating  in its leak detection system.  These
 volumes were used to  calculate the  overall liner permeability, which
 ranged from 4  x 10~8  cm/s  to 3 x 10~7  cm/s,  demonstrating that the
 original  specifications  of  1 x 10~6 cm/s had been met.

      Four of the  six  landfills,  facilities L, M, P, and Q, have continuous-
 coverage leak  detection  systems.  Liquids have been detected in the leak
 detection layers  of sites L, P,  and Q.   However, only one, site L, is
 considered  a failure.  Here, slightly  contaminated liquids were removed from
 the detection  system manhole less than 1 year after the start of operation.
 Facility Q  also had slightly contaminated liquids removed from its detection
 system.   The volume of liquid removed was used by the facility owner to
 calculate the  admixed  liner's permeability, which ranged from
 3  x ICT8 cm/s  to  6.5 x 10~8 cm/s, indicating that the liner met the
 original  permeability  specification of 1 x 10~7 cm/s.  The as-built liner
 permeability at facility P  has not been determined.  The source of small
 amounts  of  uncontaminated liquids in the detection system at this facility
 was being investigated by the site owner.  The results of this investigation
 were  not available at  this writing.

 7.7.2   Groundwater Monitoring

      Information  on Federal groundwater monitoring requirements may be found
 in "Groundwater Monitoring  Guidance for Owners and Operators of Interim
 Status Facilities" (U.S. EPA, 1983) and  in the RCRA Ground-Water Monitoring
 Technical Enforcement  Guidance Document  (U.S. EPA, 1986).

     Groundwater  monitoring wells are  the most commonly used type of
 performance  monitoring systems.  They are relatively inexpensive to install
 and maintain,  and samples are easily obtained from them.  They may be placed
 in areas  where  contamination is  estimated to be most likely to occur.  They
 may also  be  placed in  groups or  clusters with each well being at a different
 depth  and therefore monitoring the vertical as well as lateral  movement of
 any contamination.  Generally, wells are placed both upgradient and
 downgradient from a facility prior to the start of operations.   This enables
 baseline  data  for both upgradient and downgradient wells to be obtained.
 Future groundwater samples may then be compared with the baseline data and
 facility  performance can be estimated.

     Two  major  problems with relying solely on monitoring wells to determine
 facility  performance are that leachate plumes may be missed and that the
monitoring data are only qualitative.  If an adequate number of wells at
 varying depths  are  used, the possibility of missing a contaminant plume is
 greatly decreased.

     An additional problem that may occur with monitoring wells is poor
construction procedures such as the use of inappropriate materials.   This  can
                                    7-84

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 often lead to well-water contamination that is  Incorrectly attributed  to  the
 waste disposal facility.  Examples of such problems  occurred  at  sites  A and
 E.  Groundwater samples taken from the wells at site A in  1976 had  pH  levels
 between 10.7 and 11.3,  COD's of more than  3,000 ppm, and chloride levels
 greater than 1,000 ppm.  Originally, it was thought  that this contamination
 originated in the disposal facility.  A complete analysis  of  the problem,
 however,  revealed that  the monitoring wells were Improperly installed  and
 contained steel-mill  slag where clean gravel  should  have been used.  Analysis
 of samples taken from new wells,  constructed according to  the specifications,
 has not indicated elevated levels of any hazardous constituents.

      Monitoring well  analysis at  site E has shown trace levels (92  ppb
 maximum)  of 12 organic  compounds  in  the groundwater.  An investigation of
 their source indicated  that the organics most probably came from the plastic
 well  casing materials.   This case study points  out the importance of testing
 the compatibility of  all  materials with the local groundwater as well as the
 expected  leachate.

 7.7.3  Leachate Level and Quality Monitoring

      Leachate collection  systems  are designed to remove leachate that would
 otherwise accumulate  in the  liner.   By  doing  this, they prevent  the buildup
 of leachate head,  thus  keeping  liquid  infiltration into the liner to a
 minimum and therefore contributing to  the  overall performance of the liner.

      Some facilities  incorporate  leachate  level and  leachate  quality monitor-
 ing into  their overall  monitoring  program.  These parameters  serve as indices
 of the  efficiency of  treatment  methods  that they may have been used on waste
 materials and the leachate collection  system.  Analysis of the leachate may
 be used to predict  the  quality  of  the  liquid, if any,  that may be passing
 through the liner.  Leachate and  liner  samples can be  subjected  to laboratory
 compatibility tests to  indicate the  facility  performance.

 7.8  CONCLUSIONS

      The  sites  included in our  study and a  brief description  of their clay
 liners  and performance  are presented in  Table 7-1 and  are fully described in
 Section 7.2.   The  17  sites included  in  this section  were chosen because they
 illustrate a  specific performance  problem  or  facility  characteristic.  While
 conducting our  information search, we encountered many facilities both with
 and without failures  that were  not included here because they would not have
 provided  any  additional   Information.

      Comparing  the data from successful  sites with the data from leaking
 sites does not  reveal any significant differences in clay or  liner character-
 istics  that might explain  the differences in performance.  Similarly,
 performance does  not seem to  be related  to  the use of  recompacted borrow clay
 versus  recompacted native  clay  or admixed materials.  The performance of
 facilities  without recompacted  liners is, however, generally poorer than the
 performance of  facilities with a recompacted clay or admixed liner.   Also
 note  that many of the sites discussed in this section are relatively new
 (after  1975).   It is therefore difficult to state whether the  facilities
without detection systems are performing well or poorly as  sufficient time
 for leaching chemicals to  reach monitoring  wells may not have  elapsed.
                                    7-85

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 Performance  of  the  facilities that have detection systems, on the other hand,
 is much more quickly  determined than is the case with facilities I, J, L, N,
 and  Q.  Sites I,  J, L,  and N have reported performance problems.  In all
 cases, the leak detection system was instrumental in the rapid detection of
 the  performance problems.  Site Q has had small amounts of liquid detected in
 its  leak  detection  system.  The volume of liquid removed was used to deter-
 mine the  permeability of site Q's upper liner.  This value was lower than the
 design specification, indicating good performance.  Of the 17 facilities dis-
 cussed in Section 7.2,  6 have had major liner failures.  Of these six, the
 cause of  four of  the  failures is known and the cause of the failure of the
 remaining two is  unknown.  Generally, the cause of a failure in a clay-lined
 landfill  Is  very  difficult to determine because this would require removing
 the  waste and other overburden, which may in itself cause liner damage and
 Impose further  hazards.  Determining the cause of a liner failure in a lagoon
 or evaporation  pond is  somewhat less difficult because the waste is more
 easily removed.

      The  four facilities with explained failures include three lagoons or
 ponds and a  landfill  that accepted unsolidified liquids.  Two of these
 facilities had  leak detection systems; the others did not.  The failures at
 the  facilities with detection systems were noticed soon after they occurred,
 thus  preventing groundwater contamination.  The other two failures were not
 detected  until groundwater contamination was found in a monitoring well.  Two
 of the failures were due to chemical compatibility problems, one to leachate
 migration through an  improperly sealed sand seam, and the other to desicca-
 tion  cracks  that  formed in an unprotected liner.

      Sites with a single layer of clay or those relying on in situ clay for-
 mations are  less  secure since a leak cannot be detected until  pollutants are
 found in groundwater samples.  The security of a landfill  would be greatly
 Increased if  it were constructed with a continuous-coverage leak detection
 system Installed between two layers of clay.  If the Inner layer failed, the
 leak detection layer would serve as a buffer zone that might preserve the
 integrity of  the outer layer.  The use of lysimeters as a method for deter-
mining liner  performance also may provide an early indication of leachate
migration.  However, these devices are not foolproof because they are only
 able to detect leaks 1n the section of the liner directly above them.

 7.9  REFERENCES

Apgar, M., and D. Langmulr.  1971.  Groundwater pollution potential  of a
     landfill above the water table.  Groundwater 9(6):76-96.

 Bagchl,  A.  1987.  Discussion on "Hydraulic Conductivity of Two Prototype
     Liners.   ASCE Journal  of Geotechnical  Engineering, July 1987,
     113(7):796-820.

Day,  S.  R.,  and D. E.  Daniel.  1985.  Hydraulic Conductivity of Two Prototype
     Clay Liners.  ASCE Journal  of Geotechnical  Engineering,  Agust 1985,
     111(8):957-970.

Federal  Register, Monday,  July 26,  1982,  Vol.  47,  No.  143.
                                    7-86

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 Ghassemi,  M.,  M.  Haro,  and  L.  Fargo.   1984.  Assessment of Hazardous Waste
      Surface Jmpoundment  Technology  (Case Studies and Perspectives of
      Experts). Draft.  Prepared  for  the U.S* Environmental Protection
      Agency, Contract No. 68-02-3174,  Work Assignments 97 and 123.
      Multidisciplinary  Energy  and Environmental Systems and Applications,
      Torrance, California.

 Johnson, T. M., and  K.  Cartwright.   1980.  Monitoring of Leachate Migration
      in  the Unsaturated Zone in the Vicinity of Sanitary Landfills.
      Circular  514, Illinois State Geological Survey, Champaign, Illinois,
      82  pp.

 Kmet,  P.,  and  D.  W.  Lindorff.  1983.   Use of Collection Lysimeters in
      Monitoring Sanitary  Landfill  Performance.  Paper presented at the
      National  Water  Well Association Conference on the Characterization and
      Monitoring of the  Vadose  (Unsaturated) Zone, Las Vegas, Nevada,
      December  8-10.

 Rogowski,  A. S.   1986.  Hydraulic Conductivity of Compacted Clay Soils.
      In:   Land Disposal, Remedial Action, Incineration, and Treatment of
      Hazardous Waste -  Proceedings of  the Twelfth Annual  Research Symposium.
      (EPA/600/9-86/022) U.S. Environmental Protection Agency, Cincinnati,
     Ohio.  pp. 29-39.

 Rogowski, A. S., B. E. Weinrich, and D. E. Simmons.  1985.   Permeability
     assessment in a compacted clay liner.  In:   Proceedings of the 8th
     Annual Madison Waste Conference on Municipal  and Industrial  Waste,
     University of Wisconsin,  Madison,  pp.  315-336.

U.S. Environmental Protection  Agency.  1983.   Ground-water  Monitoring
     Guidance  for Owners and Operators of Interim Status  Facilities.   Office
     of Solid Waste and Emergency Response,  Washington, D.C.

U.S. Environmental Protection  Agency.  1986.   RCRA Ground-Water Monitoring
     Technical  Enforcement Guidance Document,  OSWER-9950.1,  September 1986.
     Office of Solid  Waste and  Emergency Response,  Washington, D.C.
                                   7-87

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                                   CHAPTER 8

                     PREDICTION OF CLAY LINER PERFORMANCE
 8.1  INTRODUCTION
      Although recompacted clays may have low hydraulic conductivity,  they
 are, nonetheless, permeable porous media.  If a finite depth of liquid waste
 or leachate is maintained indefinitely over a clay liner,  the liquid  and
 leachate chemicals will eventually seep through.  The goal  of transit time
 prediction is to determine both the rate of seepage with  time and  the time  it
 will take for liquids to seep through a liner.

      Generally,  transit time prediction methods may be used in  two ways.
 First,  they may be used to facilitate the design of new clay liner systems
 and second, they may be used to predict the performance of  existing clay
 liner systems and to determine the potential  for groundwater contamination
 from leachate or liquid wastes.

      Seven transit time prediction methods  are discussed in  this chapter.
 Section 8.2 is. a review of the assumptions  and basic  equations  that underlie
 the use of all  these methods.   Section  8.3  is  a discussion  of the  derivation
 and use of each  method.  Section 8.4  is  a comparison  of the  consequences—
 i.e., the predicted  transit  time,  in  years—of using  each method.

 The prediction of transit times generated by various models  cannot be com-
 pared with  any actual  liner  data because  no  information regarding  liner
 infiltration  and breakthrough  under certain conditions  is currently avail-
 able.   Section 8.5 offers a  summary and  some conclusions regarding the use of
 the different methods.  Section 8.6 is a  discussion of  the use of batch type
 adsorption  data  for  predicting  liner  performance.  References are contained
 in  Section  8.7.                                      *

 8.2 BACKGROUND  CONSIDERATIONS

 8.2.1   Performance Criteria

     In order to design or evaluate a liner system it is necessary to
 establish specific performance  criteria that will provide  a definition for
 transit  time."  These performance criteria should be designed so that, if
 they are  satisfied, the liner system will ensure safe operation over the
 intended  life of the facility or up to a certain time after closure.
 Performance criteria may be expressed 1n terms of seepage  flux (volumetric
 flow rate of seepage in a porous medium per unit cross-sectional area)
 contaminant flux (indicated by the concentration of a chemical  that is
present in the leachate), or the time taken to reach a specified flow  rate or
                                    8-1

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chemical  concentration at the bottom of the  liner.  The following are five
examples  of possible specific liner performance  criteria:

     t  Specified seepage flux at the liner  bottom

     •  Specified contaminant flux for a particular leachate component
        at the liner bottom

     •  Time taken to reach a specified seepage  flux  at the liner bottom

     •  Time taken to reach a specified leachate chemical  flux at the
        liner bottom

     •  Time taken for the concentration of  a specific  leachate  com-
        ponent to reach a specified value at the liner  bottom.

     Selection of specific performance criteria  is very important in predict-
ing corresponding "transit times," and it can also influence the applicabil-
ity of a given method.

     Recommendations regarding the use of specific performance criteria are
beyond the scope of this work.  However, examples of  the  consequences of  dif-
ferent performance criteria will be considered in the evaluation of transit
time prediction methods.

8.2.2  Clay Liner System

     The equations and boundary conditions used  in transit time  prediction
methods are based on a specific site geometry or flow domain.  This flow
domain describes the path of waste leachate  through a clay liner system.  For
the sake of this discussion it consists of,  in a vertically downward direc-
tion, saturated solid waste; a sand/gravel bed on top of  the clay liner
(leachate collection system); a clay liner;  a sand/gravel  leak detection
system; underlying local soil; and an underlying saturated aquifer  zone.
Current regulations (40 CFR 264.301(a)(2)) require a  leachate  collection  sys-
tem on top of a clay liner to maintain a leachate head  of less than 1 foot.
This makes 1t unnecessary to Include the saturated  solid  waste zone and the
leachate collection system zone in the flow domain.   The  sand/gravel  leak
detection layer may not be present in some designs.  -A  schematic of the flow
domain that is used to illustrate the transit time equations discussed below
1s shown in Figure 8-1.

     Because the hydraulic conductivity of the clay  liner material  1s much
lower than the underlying "site soil, the rate of leachate flow  is predomi-
nantly controlled by the clay liner with the underlying soil influencing  only
the boundary conditions at the bottom of the clay layer.   Some of the transit
time methods are thus based on leachate flow through  the  clay  Uner alone.
Due to the large ratio of liner width to liner depth, it  is adequate  to
consider vertical flow alone to describe the leachate flow.

     Any attenuation capacity of the clay or temporary  immobilization of  some
contaminants tends to slow the leachate migration.   Failure to account for
such factors will result in underestimates of transit time.
                                     8-2

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                                  Impounded Liquid Head
                                  in Leachate Collection Zone
                                 Clay Liner
                                 Leak Detection System
                                 Local Site
                                 Soil
                                 Saturated
                                 Aquifer
Figure 8-1.  Flow domain for leachate flow.
                     8-3

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     Note that throughout this section only aqueous leachate systems are con-
sidered; i.e._, we are considering only the flow of water and dissolved
species through the flow domain.  Although some organic-solvent-based leach-
ates may be immiscible with water, analysis of such a three-phase system (two
immiscible liquid phases + air) is extremely complex and none of the transit
time prediction methods discussed below  (except numerical methods) apply to
this situation.

8.2.3  General Equations

     A general one-dimensional equation may be used to describe the vertical
flow of fluid through the saturated/unsaturated flow domain.  The equation
may be written as follows (Bear, 1979; Huyakorn and Pinder, 1983):

                           O O, .   ^          ti>Tf
                           ,worv,I./o*1x-i                     fs  •n
                          05TT- = 5^ I.KC  Kr (^r ~ 1/J                     (°'L)
                          *dt    az   s   r  oz

     z = vertical coordinate, expressed as positive downward distance

    Ks = saturated hydraulic conductivity

    kr * relative hydraulic conductivity with respect to Ks

     * - pressure head

      - porosity

    Sw s fractional saturation (equal to  1 for saturated media)

     t = time.

     For saturated environments, the equation transforms into a steady state
formulation and one can determine the steady state flux.  For unsaturated
conditions, this equation describes the advancement of the saturated wetting
front and also the unsteady state fluid flux as a function of position.

     The general flow equation does not consider the transport of soluble
chemicals in the leachate.  A general equation to destribe the vertical
transport of a nonradioactive solute species may be written as follows
(Bear, 1979; Huyakorn and Pinder, 1983):

                                n       m 3C^
                               WC)    9  (D   )    3
                                      _    a   _
                                     9z    9z    3z
where
     D = dispersion coefficient that includes both molecular diffusion
         and mechanical dispersion

     C » solute concentration in liquid phase

     z * vertical coordinate, expressed as positive downward distance
                                     8-4

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      v = Darcian velocity in z direction
                                "s   '&         *f .-.-

      R = retardation factor to account for attenuation  capacity  of  the
          clay or soil.

      The source and sink terms are not included  because they  are not
 expected to be significant.  For  a conservative  species,  the  retardation
 factor equals 1.  The Darcian velocity,  v  (cm/s),  is  obtained from  the flow
 equation and is given by:


                              v '  -Ks  kr  
-------
methods.  A  review  of  currently available techniques is presented in "Soil
Properties,  Classifications, and Hydraulic Conductivity Testing."  (U.S. EPA,
1985)

     The  solute  transport  equation  involves two additional parameters:  a
retardation  factor and  the axial dispersion coefficient.  The retardation
factor  is dependent  upon the attenuation capacity (e.g., adsorption) of the
soil medium  and  needs to be determined experimentally.  Note also that the
attenuation  capacity of soil is time dependent and it is reduced as the soil
approaches  saturation with respect  to adsorbed species.  For conservative
liner thickness  predictions, it is  probably best to assume a retardation
factor  of unity  (no  attenuation).

     The  axial dispersion  coefficient consists of two parts:  hydrodynamic
dispersion and molecular diffusion.  The first process is caused by mixing
due to  variations in fluid velocity associated with distance from pore
walls.  Diffusion occurs in response to concentration gradients and by
random  thermal motion.  The molecular diffusion coefficient should be
readily available from  the literature, whereas measurement of the hydro-
dynamic dispersion coefficient is tedious and time consuming, and no
standardized methods are available  for this purpose.

8.3  TRANSIT TIME PREDICTION METHODS

     The  general equations describe leachate flow and solute transport in
the flow  domain  shown in Figure 8-1.  Solving these equations will give the
seepage flux, leachate  flux, moisture profiles, and concentration profiles
as a function of time.  Together with the appropriate performance criteria,
these equations may  be  used to assess the performance of an existing
facility  or  to design an effective  new facility.  These equations are com-
plex, and they can only be solved numerically; but with certain assumptions
1t 1s possible to simplify the equations and allow analytic solutions.  Each
of the  different transit time prediction methods described below uses some
form of simplification  to  achieve this end.  In a report attached as
Appendix  A to U.S. EPA  1984, Cogley et al. reviewed several transit time
equations.

8.3.1   Simple Transit Time Equation
                                                     a
     A  simple transit time equation can be used to estimate the necessary
bottom  liner thickness as  a function of the design life of an impoundment
(U.S. EPA, 1984, Appendix  A).  This equation assumes a flow domain that
includes  only a  saturated  clay liner.

     Due  to  saturated conditions, Equation (8.1) is transformed into a steady
state equation, and  the steady state Darcian velocity (cm/s) or flux
(cm3/cmzs) is given by Equation (8.3).  At the top of the liner (z = 0),
the liquid pressure head is equal to the impoundment liquid head (* » h); at
the liner bottom, z  is equal  to liner thickness (z = d).  Because the liner
1s saturated, the pressure head is taken as zero (* = 0) at the liner bottom,
assuming free drainage.  Thus,  the steady state Darcian velocity and flux,
assuming linear potential  gradient, are given by:


                                v = Ks (§ + 1)                          (8.4)


                                    8-6

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      Because the liner is assumed to be saturated,  the  seepage  flux  is
 established a_s soon as the impoundment liquid head  is established.   The  time
 taken by the leachate chemicals;at!"the top df the liner to  arrive at the
 liner bottom under steady state saturated conditions, due to  advection only,
 may be obtained by solving Equation (8.2).  Assuming D  = 0  and  R = 1,
 Equation (8.2) gives the required transit time,  t,  as:
      The liner thickness that is  required  to  achieve a  given  transit  time
 may then be obtained based on Equations  (8.4)  and  (8.5):
                    d = 0.5
                                                                         (8.6)
      Because only the  advective  transport  of  solute  is  considered when the
 solute  transport equation  is  solved,  the leachate  concentration at the
 bottom  of the liner after  the transit time would be  the same as that of
 waste leachate on top  of the  liner.   Before this transit time, the leachate
 chemical  concentration in  the seepage at the  liner bottom would be zero.
 The  leachate chemical  flux at the  liner bottom after the transit time can
 be obtained  simply by  multiplying  the seepage flux (cm3/cm2s) by the leachate
 concentration (ppm).

      The  key assumptions in this approach  are:

      •  Steady state saturated Darcian flow

      t  Pore fluid pressure at the bottom  of  the liner  is equal to atmos-
        pheric pressure; i.e., the bottom  layer of the  liner remains
        saturated indefinitely

      •  Solute transport is by advection only; i.e., there is no diffusion
        or dispersion

      •  Attenuation capacity  of the clay is ignored. *

      A  limiting  assumption  in  this approach is that molecular diffusion or
 dispersion is  not  significant  compared to  convective flux.  In view of the
 low permeability of clays and  the corresponding low  fluid velocity, the
molecular diffusion process may be a  significant factor.  Diffusion may
allow the dissolved chemicals  to migrate faster in a liner compared to
advective flow and will thus  reduce the transit time of the chemical
species.

      The simple  transit time equation is very easy to use,  however.  One
needs to know  only the saturated hydraulic conductivity of the liner
material,  its  total (or effective)  porosity,  and the leachate head at the
top of the liner.  Because  these parameters should be readily available,
                                     8-7

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 this equation provides a method to obtain  quick  estimates of  liner perfor-
 mance or required liner thickness.

 8.3.2  Modified Transit Time Equation

      Cogley et al. (U.S. EPA,  1984,  Appendix A)  modified the  simple transit
 time equation to account for effective  porosity  (0e) and the  suction potential
 at the liner bottom.   However,  other assumptions regarding steady state condi-
 tions, saturated Darcian flow in a homogeneous liner, and advective solute
 transport were made as before.

      Due to the steady state saturated  conditions, Darcian velocity and flux
 are again given by Equation  (8.3).  At  the  top of the liner (z = 0), the pres-
 sure head is given by impoundment height (* = h), and at the  bottom of the
 liner (z » d)  the pressure head is negative due  to suction (* = - hj).  When
 these boundary conditions are  incorporated  and a linear potential gradient
 assumed, the Darcian  velocity and flux  are  given by:

                                      h+h .
                              v = Ks (-g-S  + D                         (8.7)


      Equation  (8.2),  the solute transport equation, may then be solved as
 before—assuming  saturated steady state conditions and ignoring dispersion
 and  attenuation processes (D =  0  and R  = 1).  The resulting transit time for
 a  solute species  for  a given liner thickness is  given by:
                                            (h+hd+d)
                                                                        (8.8)
     The required Uner thickness for a specified leachate transit time is
then obtained as:
                     0.5
(8.9)
     Since only advective transport is considered for-solv1ng the solute
transport equation, the leachate concentration at the bottom of the liner
(after transit time) would be the same as the concentration of waste leach-
ate on top of the liner.  Before this transit time, the leachate concentra-
tion 1n the seepage at the Uner bottom would be zero.  The leachate chemi-
cal flux at the liner bottom after the transit time is given simply by
multiplying the seepage flux by the leachate concentration.

     Like the simple transit time equation, the modified equation assumes
saturated steady state conditions and negligible diffusion processes 1n
solute transport.  The incorporation of suction potential  at the liner
bottom 1s actually somewhat inconsistent with the assumption of saturated
flow since the negative pressure would induce unsaturated  conditions in
lower sections of the liner.  Although the suction potential at the bottom
is included, the higher hydraulic conductivity value corresponding to
                                     8-8

-------
saturated conditions is used in this equation.  As a result, for a speci-
fied transit time, this modified equation yields greater values for liner
thickness compared with the simple transit time equation.

8.3.3  Green-Ampt Wetting Front Model

     The transit time equations discussed above ignore both the initial,
unsaturated nature of the liner and infiltration dynamics.  Green and Ampt
(1911) derived a simple model to describe the infiltration process that has
been proposed as a method to assess liner reliability (U.S. EPA, 1984,
Appendix A).  A similar approach was also analyzed by McWhorter and Nelson
(1979) and discussed by EPA (U.S. EPA, 1983).

     The Green-Ampt model" (Green and Ampt, 1911) describes moisture movement
in unsaturated soil during ponded infiltration by assuming a sharp,
saturated wetting front moving down the soil column as a square wave.

     Above the wetting front, the soil is fully saturated, with a moisture
content, 0S, while below the wetting front the moisture content is equal to
its initial value, 8,.  At a given time, t, following establishment of the
ponded leachate head on top of the liner, the wetting front will have moved
down a certain distance, L.  Saturated flow analysis may be applied to the
saturated zone above the wetting front to determine the Darcian velocity or
flux as given by Equation (8.3).  Th