EPA/530/SW-91/051
                                             May 1991
                TECHNICAL GUIDANCE  DOCUMENT:


         INSPECTION TECHNIQUES  FOR  THE  FABRICATION

                             OF

                   GEOMEMBRANE FIELD SEAMS
             Cooperative Agreement No. CR-815692
                      Project Officers

                     Robert E.  Landreth
                       David A.  Carson
Waste Minimization, Destruction  & Disposal  Research Division
            Risk Reduction Engineering Laboratory
                   Cincinnati,  Ohio  45268
        Office of Solid Waste  and  Emergency  Response
             U.S.  Enironmental  Protection Agency
                      Washington,  D.C.
                     In cooperation with
            RISK REDUCTION ENGINEERING LABORATORY
             OFFICE OF RESEARCH AND DEVELOPMENT
            U.S. ENVIRONMENTAL PROTECTION  AGENCY
                   CINCINNATI, OHIO  45268
                                               Printed on Recycled Paper

-------
                                 DISCLAIMER
     The preparation of this document has been funded wholly by the United
States Environmental Protection Agency.  It has been subjected 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.
                                      ii

-------
                                   FOREWORD
     Today's rapidly developing and changing technologies and industrial
products and practices frequently carry with them the increased generation of
solid and hazardous wastes.  The U.S. Environmental Protection Agency is
charged by Congress with protecting the Nation's land, air, and water
resources.  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
environmental problems, measure the impacts, and search for solutions.

     The Risk Reduction Engineering Laboratory is responsible for planning,
implementing, and managing 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 research and the
user community.

     This document provides guidance for construction quality control and
construction quality assurance inspectors and related personnel  as to the
proper techniques for fabricating field seams in geomembranes.  It focuses on
six technical areas used to fabricate field seams of all  types of
geomembranes.  The presentation of this information details geomembrane
material preparation, equipment preparation, seam method evaluation through
test strips, seaming process, inspection activities after seaming, and
instructions for seaming under unusual conditions.  Rationale is provided for
the various conditions and limitations that are suggested.  A glossary of
terms relevant to the field seaming of geomembranes is provided at the end of
the document.
                                      E.  Timothy Oppelt,  Director
                                      Risk Reduction Engineering Laboratory
                                     iii

-------
                                   PREFACE


     Subtitle C of the Resource Conservation and Recovery Act (RCRA) requires
the U.S. Environmental Protection Agency (EPA) to establish a Federal
hazardous 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 Title 40 Code of Federal Regulations (40 CFR).  The principal 40
CFR Part 264 and 265 regulations were issued on July 26, 1982 for treatment,
storage, and disposal (TSD) facilities and establish performance standards for
hazardous waste landfills, surface impoundments, land treatment units, and
waste piles.  The regulations have been amended several times since then.

     In support  of the regulations, EPA has been developing three types of
documents to assist preparers and reviewers of RCRA permit applications for
hazardous waste TSO facilities.  These include RCRA Technical Guidance
Documents, Permit Guidance Manuals, and Technical Resource Documents (TRDs).

     RCRA Technical Guidance Documents, such as this one, present design and
operating parameters 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 40 CFR Part 264.

     The Technical Resource Documents present summaries of state-of-the-art
technologies and evaluation techniques determined by the Agency to constitute
good engineering designs, practices, and procedures.  They support the RCRA
Technical Guidance Documents and Permit Guidance Manuals in certain areas
(i.e., liners, leachate management, final covers, and water balance) by
describing current technologies and methods for designing hazardous waste
facilities, or for evaluating the performance of a facility design.  Although
emphasis is given to hazardous waste facilities, the information presented in
these TRDs may be used for designing and operating nonhazardous waste TSD
facilities as well.  Whereas the RCRA Technical Guidance Documents and Permit
Guidance Manuals are directly related to the regulations, the information in
these TRDs covers a broader perspective and should not be used to interpret
the requirements of the regulations.

     This document is a Technical Guidance Document prepared by the Risk
Reduction Engineering Laboratory of EPA's Office of Research and Development
in cooperation with the Office of Solid Waste and Emergency Response.  The
document has undergone extensive technical review and has been revised
accordingly.  With the issuance of this document, all previous drafts are
obsolete and should be discarded.
                                      iv

-------
     Comments are welcome at any time on the accuracy and usefulness of the
information in this document.  Comments will be evaluated, and suggestions
will be incorporated, wherever feasible, before publication of any future
revisions.  Written comments should be addressed to EPA RCRA Docket (OS-305),
401 M Street S.W., Washington, DC  20460.  The document for which comments are
being provided should be identified by title and number.

-------
                                  ABSTRACT


     This Technical Guidance Document Is meant to augment the numerous
construction quality control and construction quality assurance (CQC and CQA)
guidelines that are presently available for geomembrane installation and
inspection.  It is focused on all current methods of producing geomembrane
seams including HOPE and VLDPE, PVC, PVC-R,  CSPE, CSPE-R, CPE, CPE-R, EIA and
EIA-R.  In general, the tone of most of the existing guidelines is to allow
the installer almost complete freedom in making seams with the only
conditions being that they pass;

     (a)   destructive shear and peel tests to a stipulated strength, and
     (b)   selected nondestructive tests.

     By developing a report somewhere between the typical CQC/CQA Documents
and an installer's training manual,  i.e., a "Technical Guidance Document", it
is hoped that this document will provide meaningful insight for an inspector
as to what the installer is trying to accomplish.  At the same time it might
be also helpful to the installer in recognizing that others have an interest
in their specific activity.  After some introductory material, the manual
presents six specific methods used for fabricating field seams of the types
of geomembranes being most widely used for environmental control systems.
They are the following:

           extrusion fillet seams
           extrusion flat seams
           hot wedge seams
           hot air seams
           chemical fusion seams
           adhesive seams
                                      VI

-------
                                TABLE OF  CONTENTS
                                                                         PAGE
DISCLAIMER	ii
FOREWORD	iii
PREFACE	iv
ABSTRACT	vi
LIST OF FIGURES	x
LIST OF TABLES	xv
ACKNOWLEDGEMENTS	xvi


SECTION 1.  INTRODUCTION AND AUDIENCE 	 1

SECTION 2.  CONSTRUCTION QUALITY ASSURANCE CONCEPTS 	 5

SECTION 3.  TERMINOLOGY AND PREPARATORY ISSUES	9

     3.1   TERMINOLOGY	9
     3.2   PREPARATORY ISSUES	11
     3.3   UNITS	13
     3.4   TEST STRIPS	14

SECTION 4.  AN OVERVIEW OF FIELD SEAMING METHODS	19

SECTION 5.  DETAILS OF EXTRUSION FILLET SEAMS	23

     5.1   GEOMEMBRANE PREPARATION	23
     5.2   EQUIPMENT PREPARATION	26
     5.3   TEST STRIPS	29
     5.4   ACTUAL SEAMING PROCESS	31
     5.5   AFTER SEAMING	40
     5.6   UNUSUAL CONDITIONS	41

SECTION 6.  DETAILS OF EXTRUSION FLAT SEAMS	45

     6.1   GEOMEMBRANE PREPARATION	45
     6.2   EQUIPMENT PREPARATION	48
     6.3   TEST STRIPS	49
     6.4   ACTUAL SEAMING PROCESS	54
     6.5   AFTER SEAMING	57
     6.6   UNUSUAL CONDITIONS	58
                                      vii

-------
                         TABLE OF CONTENTS (continued)
                                                                         PAGE
SECTION 7.  DETAILS OF HOT WEDGE SEAMS	63

     7.1   GEOMEMBRANE PREPARATION	63
     7.2   EQUIPMENT PREPARATION	66
     7.3   TEST STRIPS	71
     7.4   ACTUAL SEAMING PROCESS	73
     7.5   AFTER SEAMING	78
     7.6   UNUSUAL CONDITIONS	80

SECTION 8.   DETAILS OF HOT AIR SEAMS	85

     8.1   GEOMEMBRANE PREPARATION	85
     8.2   EQUIPMENT PREPARATION	91
     8.3   TEST STRIPS	95
     8.4   ACTUAL SEAMING PROCESS FOR THE MANUAL, HAND-HELD TYPE
           OF HOT AIR SEAMING	97
     8.5   ACTUAL SEAMING PROCESS FOR THE AUTOMATED,  MACHINE-DRIVEN
           TYPE OF HOT AIR SEAMING	101
     8.6   AFTER SEAMING	103
     8.7   UNUSUAL CONDITIONS 	 105

SECTION 9.  DETAILS OF CHEMICAL AND BODIED CHEMICALLY FUSED SEAMS .... 109

     9.1   GEOMEMBRANE PREPARATION	109
     9.2   EQUIPMENT PREPARATION	114
     9.3   TEST STRIPS	116
     9.4   ACTUAL SEAMING PROCESS 	 121
     9.5   AFTER SEAMING	126
     9.6   UNUSUAL CONDITIONS 	 128

SECTION 10.  DETAILS OF CHEMICAL ADHESIVE SEAMS 	 132

     10.1   GEOMEMBRANE PREPARATION 	 132
     10.2   EQUIPMENT PREPARATION 	 137
     10.3   TEST STRIPS	139
     10.4   ACTUAL SEAMING PROCESS	144
     10.5   AFTER SEAMING	149
     10.6   UNUSUAL CONDITIONS	152
                                      viii

-------
                         TABLE OF CONTENTS (concluded)

                                                                         PAGE


SECTION 11.  EMERGING TECHNOLOGIES FOR GEOMEMBRANE SEAMING	156

     11.1   ULTRASONIC SEAMS	156
     11.2   ELECTRICAL CONDUCTION SEAMS 	 158
     11.3   MAGNETIC INDUCTION SEAMS	158

SECTION 12.  REFERENCES 	 162

SECTION 13.  GLOSSARY OF TERMS	166
                                      ix

-------
                               LIST OF FIGURES
FIG. NO.                                                                 PAGE
3.1    Test strip process flow chart 	 16
5.1    Type of hook blade used for the cutting of liner materials	24
5.2    Hand-held electric rotary grinder with circular disc grit
       grinding paper  	 27
5.3    Photographs of various types of extrusion fillet welding
       devices	28
5.4    Test strip process flow chart	30
5.5    Fabrication of geomembrane seam test strip	32
5.6    Preparing the bevel of the upper geomembrane for liner
       thicknesses greater than 1.5 mil  	 34
5.7    Proper orientation and grinding preparation of sheets prior
       to tacking and extrudate placement  	 35
5.8    Photographs of different orientations of grinding patterns	36
5.9    Photographs of different extent of grinding patterns after
       extrusion fillet seaming  	 38
5.10   Smooth propping wedge used when tacking of sheets is done
       before surface grinding of geomembrane sheets 	 39
5.11   Schematic diagrams of various cross sections of extrusion
       seams	39
5.12   Photographs of cross sections of various types of HOPE
       extrusion fillet seams  	 42
6.1    Type of hook blade used in the cutting of liner materials 	 47
6.2    Grinding locations and method used in the preparation of
       extrusion flat seams	49
6.3    Test strip process flow chart 	 51

-------
                          LIST OF FIGURES  (continued)
FIG. NO.                                                                 PAGE
6.4    Fabrication of geomembrane seam test strip	52
6.5    Photographs and schematic diagram of extrusion flat seaming
       of geomembrane sheets  	 56
6.6    Schematic diagram of cross section of extrusion flat seam
       with extrudate out to  the edge of the upper geomembrane 	 57
6.7    Photographs of cross sections of HOPE extrusion flat seams	59
7.1    Type of hook blade used in the cutting of liner materials 	 65
7.2    Various types of hot wedge seaming devices  	 68
7.3    Diagrams of the hot wedge elements upon which the two sheets
       to be joined are passed	69
7.4    Test strip process flow chart 	 72
7.5    Fabrication of geomembrane seam test strip	74
7.6    Details of the hot wedge system showing relative positions of
       the hot wedge, rollers and sheets to be joined	76
7.7    Hot wedge T-seam detail 	 79
7.8    Schematic diagram of cross section of dual (split) hot wedge
       seam illustrating squeeze-out 	 80
7.9    Photographs of cross sections of HOPE hot wedge seams 	 81
8.1    Trimming of excess geomembrane to obtain proper overlap prior
       to seaming	87
8.2    Type of scissors recommended for cutting geomembranes 	 87
8.3    Photographs of "fishmouth" and its correction and patching  .... 88
8.4    Various types of hot air seaming devices  	 92
8.5    Cross section of automated machine-driven hot air seaming
       device for geomembranes 	 94
8.6    Test strip process flow chart 	 96
                                      xi

-------
                          LIST  OF  FIGURES  (continued)
FIG. NO.                                                                 PAGE

8.7    Fabrication of geomembrane seam test strip  	 98
8.8    Fabrication of a field seam using manual hand-held hot air
       seaming technique	100
8.9    Fabrication of a field seam using automated,  machine-driven
       hot air seaming technique	102
8.10   Dual track hot air machine T-seam detail for HOPE or VLDPE	104
8.11   Schematic diagrams of cross sections of single and dual
       hot air seams illustrating squeeze-out	105
8.12   Cross sections of EIA liner seams fabricated by the hot air
       method showing left, center, and right sides of completed
       seam    	106
9.1    Trimming of excess geomembrane to obtain proper overlap prior to
       seaming	Ill
9.2    Photographs of a "fishmouth" and its correction and patching. .  .  .112
9.3    Photograph of squirt bottles and method of application	115
9.4    Photograph of types of rollers used to apply pressure to
       chemically bonded seams	116
9.5    Test strip process flow chart	118
9.6    Photographs of preparation of a field test strip prior to
       production seaming	119
9.7    Positioning of wooden "seaming board" beneath seam area of
       liner to provide for a uniform and smooth subsurface	122
9.8    Perspective diagram of locations where "T" configurations
       commonly occur	123
9.9    Photograph of "T" trimming tool  shaving the upper surface
       of an existing seam in preparation of new intersecting seam . .  .  .123
9.10   Application of fusion chemical	125
                                     xii

-------
                          LIST  OF  FIGURES  (continued)
FIG. NO.                                                                 PAGE

9.11   Initial rolling motion parallel to seam for the fabrication
       of chemically fused seams of PVC liners	125
9.12   Photographs of air lance and pick testing of completed seam .  .  .  .127
9.13   Cross sections of PVC liner seams fabricated by the chemical
       fusion seaming method showing left, center, and right sides
       of completed seam	129
10.1   Trimming of excess geomembrane to obtain proper overlap prior
       to seaming and types of scissors recommended for cutting of
       geomembranes	134
10.2   Photographs of a "fishmouth" and its correction and patching  .  .  .135
10.3   Photograph of types of rollers used to apply pressure to
       bodied fusion chemical seams	138
10.4   Test strip process flowchart	141
10.5   Photographs of preparation  of a field test strip prior to
       production seaming	142
10.6   Positioning of wooden seaming board beneath seam area	145
10.7   Perspective diagram of locations where "T" configurations
       commonly occur	147
10.8   Photograph of "T" trimming  tool shaving the upper surface of an
       existing seam in preparation of new intersecting seam	147
10.9   Initial rolling motion parallel to seam for the fabrication
       of adhesive seams for CEP,  CSPE or PVC liners	148
10.10  Photographs of air lance and pick testing of completed seam .  .  .  .150
10.11  Cross section of CSPE-R liner seams fabricated by the
       chemical adhesive seaming method	151
11.1   Schematic diagrams of ultrasonic welding of plastic
       (and metal) sheets	157
                                     XI11

-------
                         LIST OF FIGURES  (concluded)

FIG. NO.                                                                 PAGE


11.2   Schematic diagram of rollers,  ultrasonic horn and geomembrane
       sheets in the ultrasonic seaming process	157

11.3   Schematic diagram of an electrofusion pipe coupling
       process	159

11.4   Schematic diagram of the electrical conduction method of
       joining geomembrane	159

11.5   Schematic diagram of the magnetic induction method of
       joining geomembranes	160
                                      xiv

-------
                                LIST OF TABLES
TABLE NUMBER                                                             PAGE

3.1   Polyethylene Types 	 10
3.2   Compounded Thermoplastics and Thermoplastic Elastomers 	 10
4.1   Fundamental Methods of Joining Polymeric Geomembranes  	 18
4.2   Most Commonly Used Field Seaming Methods for Various
      Geomembranes 	 20
7.1   Temperature Ranges for Hot Wedge Seaming of Thermoplastic
      Geomembranes 	 70
8.1   Typical Temperature Ranges for Hot Air Seaming of
      Geomembranes 	 93
                                      xv

-------
                               ACKNOWLEDGEMENTS


     This technical guidance document grew out of a series of meetings of
various manufacturers of geomembranes.   Drafts were reviewed by the
manufacturers, fabricators and installers of geomembranes, private consultants
and owners of waste management facilities.  Robert M.  Koerner, Director of the
Geosynthetic Research Institute,  was the project coordinator who extends
sincere appreciation for the cooperation of this group of organizations in
sharing information and critiquing the various drafts  of the document.

     The EPA project manager of this technical guidance document was
Robert E. Landreth with the assistance of David A. Carson.  The authors wish
to thank Donna A. Zunt, the preparer of the manuscript.
                                      xv i

-------
                                   SECTION 1

                           INTRODUCTION AND AUDIENCE


     The lining and capping of hazardous  and nonhazardous solid waste
landfills, surface impoundments and waste piles is a critical component in the
prevention of contamination of subsurface soil and groundwater.  When a solid
or liquid contaminant is being contained, every aspect of the lining and
capping system must undergo the closest possible scrutiny.  The need for both
construction quality control (CQC) and construction quality assurance (CQA)
becomes requisite at many facilities.  With an extremely large number of waste
management construction and closure projects currently being planned and/or
already under construction there also comes many organizations with a lack of
experience in specialized topics.  Certainly an area such as geomembranes made
from thermoplastic polymers falls into this category.  Many inspection firms
entering into this area have had little formal training or practical
experience in dealing with geomembranes.  This is not to say that experienced
firms are not available; they are indeed, and are very active in providing
excellent inspection services.  However, there appears to be a need to have a
primer on certain aspects of geomembrane  seaming which this document will
fulfill.

     This manual is very narrowly focused, addressing only one part of the
total liner or final cover systems, that being field seaming methods for
geomembranes.  This manual assumes that the design has been completed and the
material has been selected based on site specific functions and conditions.
In this report all types of currently used geomembrane materials will be
considered.  They will be viewed with their customary method of seaming, and
not from a materials classification.  For example, for the hot wedge seaming
method, focus will be on the idiosyncrasies of the method not the fact that
most geomembranes can be seamed by this method.  When information is required
to distinguish between details such as seaming temperature from one
geomembrane to another, it will be elaborated upon accordingly.  Still
further, it is the making (or fabrication) of the seams which will be the
focus, not their destructive or nondestructive testing.  There are numerous
excellent documents on this latter topic, see, for example, Frobel (1),  Lord,
et al. (2), Overmann (3) Richardson (4), Haxo and Kamp (5), Peggs (6), etc.

     This Technical Guidance Document is primarily intended for engineering
organizations performing third-party inspection of geomembrane field seams.
This activity falls under the category of Construction Quality Assurance
(CQA).  It is generally performed by engineering design firms, engineering
testing organizations and (occasionally) by manufacturer/installers who are
separated from the Construction Quality Control (CQC) activities.  The
document has obvious overlaps with both public and private owner/operator

-------
concerns and can be used to amplify and extend their standard CQC/CQA
Documents on an as-required basis.

     When using the document for the first time, the reader should become
familiar with the introductory material included in Sections 1 to 4.  In these
sections various clarifications of terminology, definitions, departures from
current practice and other matters are described.  Following this introductory
material, however, the user should proceed directly to the section on field
seaming that is of direct interest.  Each of these sections, i.e., Section
Nos. 5 to 10, are written in a "stand-alone" fashion.  Thus repetition within
these different sections was necessary to avoid "flip-flopping" between
sections.  Of course, if one cares to read the manual in its entirety, it
becomes a tutorial on all of the currently available geomembrane seaming
methods.  Section 11 pertains to seaming technologies currently under
development.

     This Technical Guidance Document provides a field CQA person with a
readily accessible set of details of the essential aspects of the field
seaming procedure under concern.  It also provides, in as much as possible,
the explanation for stating these details.  By following its guidance it is
hoped that the manual's user will be better aware of what the installer is
trying to achieve and the rationale for performing any specific activity.  The
document does not purport to be an installers procedural manual on how to
physically make geomembrane field seams.  There are numerous CQC manuals
available by manufacturer/installer organizations as well as owner/operator
organizations for that purpose.

-------
FIELD NOTES:

-------
FIELD NOTES:

-------
                                   SECTION 2

                    CONSTRUCTION QUALITY ASSURANCE CONCEPTS


     As written in EPA Report 600/2-88/052 entitled "Lining of Waste
Containment and other Impoundment Facilities" (7) construction quality
assurance (CQA) is a planned system of activities that provides assurance that
the unit is constructed as specified in the design.  Thus, CQA refers to those
activities initiated by the owner of the facility to ensure that the
construction of the entire facility, including manufacture, fabrication, and
installation of the various components of the lining and final cover systems,
meets design specifications and performance requirements.  The activities
include inspections, verifications, audits, and evaluations of materials and
workmanship necessary to determine and document the quality of the constructed
facility.  These activities are often performed by an owner/operator contracted
third-party quality assurance team that is independent of the designer,
manufacturer, fabricator, and installer to ensure impartiality.

     It should be noted that Construction Quality Control (CQC) and
Construction Quality Assurance (CQA) are often loosely used terms covering the
entire range of construction activities.  They are, however, used quite
rigorously in this Technical Guidance Document.


         Construction Quality Control (CQC), or simply Quality Control, refers
          to activities conducted by the manufacturer and/or installer to bring
          to bear the highest quality construction activities for the situation
          under concern.  In this manual, it is the fabrication of geomembrane
          field seams.  There often will be a separate document to define and
          elaborate on the various details.  This document is usually developed
          "in-house", in that it is voluntarily offered to show the degree of
          seriousness to which the manufacturer/installer intends to go about
          the construction of the geomembrane field seams.  It will be referred
          to as the "CQC Document."

         Construction Quality Assurance (CQA), or simply Quality Assurance,
          is completely separate from CQC.  It cannot be done by the same
          individuals or even the same organizations.  It is often referred
          to as "third party" inspection suggesting that an organization, or
          persons, not affiliated with the owner/operator or manufacturer/
          installer is performing the inspection activities.  This is the
          intended audience for this Technical Guidance Document.  The
          formation of such a CQA activity, and the role it has in the
          inspection of geomembrane field seams, is defined in a document
          which will be referred to in this manual as the  "CQA Document."
          CQC and CQA will obviously overlap in many instances.  The ultimate

-------
        case geomembrane field seams.  The separate documents, referred to
        herein collectively as "CQC/CQA Documents," should be synchronized
        with one another.   Any differences between the two documents, or
        between these two documents and the contract plans and
        specifications must be addressed at a Pre-Construction meeting.  All
        parties involved must be aware that this Pre-Construction meeting is
        where the "ground rules" for construction will occur and all parties
        will thereafter perform and act accordingly.

     Regarding the elements of a CQC/CQA Document, EPA Report 530-SW-86-031
(NTIS PB87-132825) entitled "Construction Quality Assurance for Hazardous
Waste and Land Disposal Facilities" (8) presents the following key elements:


        Responsibility and Authority - The responsibility and authority of
         organizations and personnel involved in permitting, designing, and
         constructing the facility should be described in the CQC/CQA
         Documents.

        CQA Personnel Qualifications - The qualifications of the CQA
         officer and supporting CQA inspection personnel should be presented
         in the CQC/CQA Documents.

        Inspection Activities - The observations and tests that will be
         used to ensure that the construction or installation meets or
         exceeds all design criteria, plans, and specifications for each
         component should be described in the CQC/CQA Documents.

        Sampling Strategies - The sampling activities, sample size, methods
         for determining sample locations, frequency of sampling, acceptance
         and rejection criteria, and methods for ensuring that corrective
         measures are implemented should be presented in the CQC/CQA
         Documents.

        Documentation - Reporting requirements for CQA activities should be
         described in detail in the CQC/CQA Documents.


     This particular guidance document focuses on one specific aspect of CQA
namely the inspection of the fabrication of field seams used in the joining
of the most commonly used geomembranes.

-------
FIELD NOTES:

-------
FIELD NOTES:

-------
                                  SECTION 3

                      TERMINOLOGY AND PREPARATORY ISSUES


     The design of a geomembrane for a lined facility involves a substantial
amount of work before the actual construction is performed.  In order that
the reader understands and appreciates the importance of some of these
preactivities, it was felt that a section on historical and future
perspectives, including assumptions, was needed.  The authors have also
attempted to standardize or clarify terminology to more accurately reflect
current industry practice.


3.1  TERMINOLOGY

     Many polymers commonly used in the manufacture of geomembranes,
previously called flexible membrane liners (FML), have been inaccurately
named, titled and described.  Polymeric resins and processing methods evolve
over time to provide products that will serve their intended design function
better over long periods of time.  As more products become available, it is
important to understand the proper descriptions for various polymeric
geomembrane materials.

     In current practice, the term "high density polyethylene (HOPE)" is
used to describe geomembranes whose base resin may actually be medium
density polyethylene (MDPE).  There are several  resins of different
densities currently used in the manufacture of polyethylene geomembranes,
see Table 3.1.

     The density ranges on Table 3.1 are for the basic polymer,  i.e. the
resin, before addition of carbon black and other additives to either
increase performance and durability or assist in production.  This document
will utilize the ASTM designation HOPE to reflect the material  in use today.
Very low density polyethylene (VLDPE) resin falls into the density range
below 0.910 g/cc and is not yet designated by ASTM.

     Some geomembrane sheets are compounded versions of relatively rigid
thermoplastic polymers, such as polyvinyl chloride (PVC).   Other
geomembranes are compounded versions of elastomers, such as chlorosulfonated
polyethylene (CSPE).   Each is formulated with specific expectations in mind
ranging from long-term flexibility,  to long-term weatherability,  to cost.
The authors will  utilize the terminology "compounded thermoplastic" or
"thermoplastic elastomers" to reflect the actual  material  in use today.
Table 3.2 lists several of these liner materials that are  in current use.

-------
                      TABLE 3.1.  POLYETHYLENE TYPES.
Acronym
HOPE
HOPE
MDPE
LDPE
	
Type
High Density Polyethylene
High Density Polyethylene
Medium Density Polyethylene
Low Density Polyethylene
Not designated
Nominal
Density Range
> 0.960 g/cc
0.941 to 0.959 g/cc
0.926 to 0.940 g/cc
0.910 to 0.925 g/cc
< 0.910 g/cc
ASTM
D 1248
Type
IV
III
II
I
0
 * Uncolored,  unfilled material



    TABLE 3.2.  COMPOUNDED THERMOPLASTICS AND THERMOPLASTIC ELASTOMERS.*



                           PVC            EIA

                           PVC-R**         EIA-R

                           CPE            CSPE

                           CPE-R          CSPE-R
    See Section 13,  Glossary of Terms  for definitions.
    "R"  denotes  fabric reinforced geomembrane.


     Resins used in pipes, fittings and appurtenances are generally
significantly different from those used in the manufacture of geomembranes.
While prefabricated boots may make installation more convenient, it may not
be possible to seam geomembranes directly to these other items.  Further,
the junction is generally fortified with a mechanical connection to ensure a
flexible watertight bond.  These details must be clearly stipulated in the
CQA/CQC Documents.

     One of the fundamental methods of joining polymer geomembrane sheets is
with a chemical processes of chemical  fusion or chemical-adhesive methods.
Commonly referred to as "solvent welding," or "solvent seaming," a more
generic term "chemical bonding" will be used in this document.  The methods

                                     10

-------
and materials used to perform this type of bonding can vary widely, and may
vary in accordance with site conditions.  The designer should evaluate these
variances and incorporate them into the CQC/CQA Documents.

     Workers and inspectors should protect themselves from long-term
exposure to the chemicals present during any installation.  The safety
precautions printed on the labels of all chemicals should be followed.
Personal protective equipment should exceed the minimal requirements listed
on the labels.  Material Safety Data Sheets should also be reviewed prior to
exposure.  State and local safety regulations should be followed.

     Workers and inspectors should also be aware that some seaming devices
can and do get very hot.  These devices require the use of extension cords
which could cause personnel to trip and fall.  Hot air/gas seaming devices
or other air blowing devices may cause dirt to be blown into eyes.  All
appropriate state and local safety regulations should be followed.

     Following conventional usage, the term "hot air" has been used when
speaking of the process involving hot gas to seam geomembrane sheets.
Certain unusual circumstances may require the use of an alternate heat
conveyance gas other than air.  The use of such an alternative must be
clearly stated in the CQC/CQA Documents.


3.2  PREPARATORY ISSUES

     This document is intended to provide guidance for the inspection of
geomembrane seams being fabricated in the field.  To this end, several
assumptions have been made regarding the actual material brought or
delivered to the installation site.  This document assumes that the facility
design has been completed, the material has been selected based on specific
site functions and conditions and that CQC/CQA Documents have been
developed.

     Inherent in these broad assumptions are the following items:

     (1)   The designer should prequalify the material and seaming
           technique, before the actual installation, and include in the
           CQC/CQA Documents evaluation procedures to verify the quality of
           the actual seams.  In these cases such concerns as stress
           cracking and/or chemical resistance of the geomembrane sheet and
           seams, or percentage of full seam strength could be resolved.
           The prequalifying period may also be used to correlate
           accelerated (e.g. oven) aging of chemical seams with full seam
           strength without acceleration.  However, these prequalification
           tests are to be used only for general acceptance as the actual
           field seam should be accepted/rejected based on actual field
           samples based on the CQC/CQA Documents.

     (2)   The soil subgrade has been prepared such that no rocks, sticks,
           sudden elevation changes,  etc., are present to damage the
           geomembrane sheet by puncturing from below or from damage

                                     11

-------
      resulting from installation personnel  walking  or equipment (e.g.,
      rubber tired generators)  being on  top  of the geomembrane.

(3)    The design considered the appropriate  thickness  of the material
      being installed.   This includes but  is not  limited to:  minimum
      regulatory material  requirements;  thickness variation  due  to
      manufacturing; thickness  changes due to material  preparation
      (grinding or softening geomembrane surface  layers) and design
      requirements.  It is recognized that the seam  areas can be the
      weak points in the geomembrane system.  The design should  consider
      the above factors independently and  jointly as they may result in
      stress concentrations.

(4)    The facility design  includes consideration  for durability  of the
      material.  Service life of the geomembrane  may be affected by seam
      cracking or mechanical fatigue that  may cause  cracking or
      catastrophic failure; swelling and softening of  polymeric
      components due to absorbed waste constituents  combined with an
      overburden load that may  cause creep-induced damage; and
      extraction, volatilization, or biodegradation  of additives in the
      compounds due to long-term exposure  that may cause degradation of
      polymeric materials.

(5)    The design has taken site specific conditions  such as  potential
      temperature and humidity  into consideration when selecting the
      geomembrane material to be installed and the actual  seaming
      technique to be used at that specific  site. When seaming
      geomembrane sheet it is actually the sheet  temperature that
      influences the quality of the seam.  It is, therefore,  recommended
      that geomembrane sheet temperature be  measured rather  than ambient
      temperature.

(6)    It is also recognized that moisture  can cause  a  detrimental effect
      on seam quality.   In those cases where chemicals are used  to make
      the seam the designer should understand that the process of
      evaporation of the chemical involves the consumption of heat (heat
      of vaporization)  from the geomembrane  being seamed and thus can
      cool  the geomembrane surface resulting in moisture condensation  in
      the seam area when the relative humidity is high.  The point is
      that temperature and humidity at the time of installation  may
      affect the selection of the chemical mixture used.  This same heat
      phenomenon will also cause condensation in  seam  areas  for  hot
      wedge and extrusion  welds.

(7)    Grinding of sheet edges in preparation for  extrusion welding
      should always be done to  leave marks perpendicular to  the  sheet
      edge, to the extent  possible.  Insufficient data exists to
      definitively determine whether all grind marks should  be covered.
      It is generally recognized that they should, but it is also known
      that extrudate over  unground area  will not  form  a good bond.  The
      designer should specify or recommend which  procedure will  be
      acceptable and how to evaluate this  through the  CQC/CQA Documents.

                                 12

-------
    (8)   The number and spacing of destructive tests in production seams
          has been clarified and stipulated in the CQC/CQA Documents.  This
          includes the length of the destructive test sample, how sections
          are distributed, when and to whom test results are due, and
          acceptance/rejection criteria.

    (9)   The CQC/CQA Documents should be very specific when new to old
          sheets are being seamed in the field, when different thicknesses
          of the same sheet are being seamed together, when different
          materials are seamed together (e.g. PVC and CSPE, VLDPE and HOPE,
          etc.), when sheet is bonded or joined to pipes, manholes, and/or
          other appurtenances, or for other unusual conditions.

    (10)  The design and CQC/CQA Documents have determined the number,
          length, distribution and testing of seam test strips.  One could
          envision individual samples for the owner/operator for site
          approval, the geomembrane manufacturer, for archive purposes and
          for the regulatory community.  All of these requirements may
          result in test strip lengths from 1.5 to 4.5 m (5 to 15 ft.) or
          more.  The length should be determined based on which ASTM test
          will be used for seam evaluation as well as the number of
          interested parties; in any case the total length should be
          specified in the CQC/CQA Documents.  The implications of failure
          of these test strips must be clearly understood by all parties.


3.3  UNITS

     In past EPA documents, all dimensions in the text,  tables and figures
have been traditional, or English units, i.e., the "foot-pound-degree
Fahrenheit" system of measurement.  The future, as we all know, is toward
the use of metric units, i.e., the "meter-gram-degree Centigrade" system.
This latter system has been slightly revised into the ("Systeme
Internationale d'Units") units or simply "S.I." units and is rapidly being
accepted on a worldwide basis.

     This manual is written in dual units with the S.I.  units as the
preferred units and the standard units following in parenthesis.  It is more
than likely that future EPA documents will be in S.I. units only, thus a
complete familiarization will eventually be necessary.

     A word of explanation as to unit of length is necessary.  The S.I. unit
of length is the millimeter (mm).  Recognize that it is  a very small value,
i.e.,  1 mm - 0.04 inches.  Thus the coverage of a 6 inch patch over a hole
in a geomembrane would convert to 150 mm.   Note that the tolerance of this
value should be considered equivalently, i.e. we are not inferring a
tolerance of 1 mm,  but the usual  tolerance of say 1 inch which would be
approximately 25 mm.   Thus to ease the unfamiliar reader into S.I. units we
have written the text in centimeters so as to take the customary values of
tolerance into account.   The figures,  however, have been labeled in


                                     13

-------
millimeter and meter units which are the recommended S.I. values to use and
rounded for convenience.

     With regular use of S.I. units and thinking in this manner, the
differences between mm, cm, and m values will  become routine.


3.4  TEST STRIPS

     Test (or trial) strips, also called qualifying seams, are considered to
be an important aspect of CQC/CQA procedures.   They are meant to serve as a
prequalifying vehicle for personnel, equipment and procedures for making
seams under identical material and climatic conditions as will be the actual
production field seams.  The test strips are usually made on two narrow
pieces of excess geomembrane varying in length between 1.5 to 4.5 m (5 to 15
ft.).  The test strips should be made in sufficient lengths, preferable as a
single continuous seam, for all required purposes.

     The goal of these activities is to imitate all aspects of the actual
production field seaming activities intended to be performed in the
immediately upcoming work session to estimate seam quality.  Ideally, test
strips can estimate the quality of the production seams while minimizing
damage to the installed geomembrane through destructive mechanical testing.
They are typically made every 4 hours (for example, at the beginning of the
work shift, after the lunch break) or whenever personnel or equipment
changes and when climatic conditions reflect wide changes in geomembrane
temperature (5C [ 9 F]  change  in  one hour) or  other  conditions  that
could affect s2eam quality.  These details, including the minimum level of
destructive testing of the production field seams should be stipulated in
the Contract Specifications or CQC/CQA Documents.

     The destructive testing of the test strips in shear and peel should be
done as soon as the installation contractor feels that the strength
requirements of the Contract Specification or CQA/CQA Documents can be met.
This is generally done at the site using a field tensiometer.  Thus it
behooves the contractor to have all aspects of the test strip seam
fabrication in complete working order just as would be done in the case of
fabricating production field seams.

     In the flow chart following it is seen that failed test strips are
linked to an increased frequency of destructive tests to be taken on
production field seams made during the time interval between making the test
strip and its testing.  Furthermore, it is seen that there are only two
chances at making adequate test strips before production field seaming is
stopped and repairs are initiated.  The specifics of these repairs are not
defined in this document.  They should be covered in either the Contract
Specification or the CQC/CQA Documents.

     Additional text for conducting these tests is located in each of the
specific seam focused sections and generally follows the activity pattern
described in Figure 3.1.


                                     14

-------
                      Not*: Stunlng dm filling Ib Pnpir*
                       Acctplfb/* TtitStrtptMlyRiqvtn
                       ROnlnlng In Aecoaltnct wHn CQC/COA Daeumum
Figure  3.1   Test  strip  process flow  chart.
                         15

-------
FIELD NOTES:
                                      16

-------
                                  SECTION 4

                      AN OVERVIEW OF FIELD SEAMING METHODS


     The fundamental mechanism of joining polymer geomembrane sheets is to
temporarily reorganize the polymer structure of the two surfaces in a
controlled manner (i.e. melt or soften) that, after the application of pressure
and after the passage of a certain amount of time, results in the two sheets
being bonded together.  This reorganization results from an input of energy
that originates from either chemical or thermal processes.  These processes may
involve the addition of extra polymer in the bonded area.

     Ideally, seaming two geomembrane sheets would result in no net loss of
tensile strength across the two sheets and the joined sheets would perform as
one single geomembrane sheet.  However, due to stress concentrations resulting
from the seam geometry, current seaming techniques may result in minor tensile
strength loss compared to the parent geomembrane sheet.  The characteristics of
the seamed area are a function of the type of geomembrane and the seaming
technique used.  These factors, such as residual strength, geomembrane type,
and seaming type, should be recognized by the designer when applying the
appropriate design factors of safety for the overall geomembrane function and
facility performance.

     It should be noted that the seam can be the location of the lowest tensile
strength in a geomembrane liner.  Designers and inspectors should be aware of
the importance of seeking only the highest quality geomembrane seams.   The
minimum seam tensile strengths (as determined by design) for various
geomembranes must be predetermined by laboratory testing, knowledge of past
field performance, manufacturers literature, various trade journals or other
standard setting organizations that maintain current information on seaming
techniques and technologies.

     The methods of seaming at the time of the printing of this document and
discussed herein are shown in Table 4.1.

     Within the entire group of thermoplastic geomembranes that will be
discussed in this manual, there are four general categories of seaming methods:
extrusion welding, thermal fusion or melt bonding,  chemical  fusion and
chemical adhesive seaming.   Each will  be explained along with their specific
variations so as to give an overview of field seaming technology.

     Extrusion welding is presently used exclusively on geomembranes made from
polyethylene.   A ribbon of molten polymer is extruded over the edge of,  or in
between, the two surfaces to be joined.  The hot extrudate causes  the  surfaces
of the sheets to become hot and melt, after which the entire  mass  then cools
and bonds together.   The technique is called extrusion fillet seaming  when the

                                       17

-------
       TABLE 4.1.  FUNDAMENTAL METHODS OF JOINING POLYMERIC GEOMEMBRANES



           Thermal Processes                     Chemical  Processes


       Extrusion Fillet (Ch. 5)              Chemically Fused:

       Extrusion Flat (Ch. 6)                .  Chemical (Ch. 9)

       Hot Wedge (Ch. 7)                     .  Bodied Chemical (Ch. 9)

       Hot Air (Ch. 8)                       Chemical  Adhesive (Ch. 10)
extrudate is placed over the leading edge of the seam, and is called extrusion
flat seaming when the extrudate is placed between the two sheets to be joined.
It should be noted that extrusion fillet seaming is essentially the only method
for seaming polyethylene geomembrane patches and in poorly accessible areas
such as sump bottoms and around pipes.  Temperature, pressure, and seaming rate
all play important roles in obtaining an acceptable bond; too much melting
weakens the geomembrane and too little melting results in inadequate flow
across the seam interface and in poor seam strength.  The polymer used for the
extrudate is also very important and is usually the same polyethylene compound
that was used to made the geomembrane.  The designer should specify acceptable
extrusion compounds and how to evaluate them in the CQC/CQA Documents.

     There are two thermal fusion or melt-bonding methods that can be used on
all thermoplastic geomembranes.  In both of them, portions of the opposing
surfaces are truly melted.  This being the case, temperature, pressure, and
seaming rate all play important roles in that too much melting weakens the
geomembrane and too little melting results in poor seam strength.  The hot
wedge or hot shoe method consists of an electrically heated resistance element
in the shape of a wedge that travels between the two sheets to be seamed.  As
it melts the surface of the sheets being seamed, a shear flow occurs across the
upper and lower surfaces of the wedge.  Roller pressure is applied as the two
sheets converge at the tip of the wedge to form the final seam.  Hot wedge
units are automated as far as temperature, amount of pressure applied and
travel rate.  A standard hot wedge creates a single uniform width seam while a
dual hot wedge (or "split" wedge) forms two parallel seams with a uniform
unbonded space between them.  This space can be used to evaluate seam quality
and continuity of the seam by pressurizing the space with air and monitoring
any drop in pressure that may signify a leak in the seam.
                                       18

-------
     The hot air method makes use of a device consisting of a resistance
heater, a blower, and temperature controls to blow hot air between two sheets
to melt the opposing surfaces.  Immediately following the melting of the
surfaces, pressure is applied to the seamed area to bond the two sheets.  As
with the hot wedge method both single and dual seams can be produced.  In
selected situations, this technique will be used to temporarily "tack" weld two
sheets together until the final seam or weld is accepted.

     Regarding the chemical fusion seam types; chemical fusion seams make use
of a liquid chemical applied between the two geomembrane sheets to be joined.
After a few seconds to soften the surface, pressure is applied to make complete
contact and bond the sheets together.  As with any of the chemical seaming
processes to be described, a portion of the two adjacent materials to be bonded
is truly transformed into a viscous phase.  Too much chemical will weaken the
adjoining sheet, and too little chemical will result in a weak seam.  Bodied
chemical fusion seams are similar to chemical fusion seams except that 1-10% of
the parent lining resin or compound is dissolved in the chemical and then is
used to make the seam.  The purpose of adding the resin or compound is to
increase the viscosity for slope work and/or adjust the evaporation rate of the
chemical.  This viscous liquid is applied between the two opposing surfaces to
be bonded.  After a few seconds, pressure is applied to make complete contact.
Chemical adhesive seams make use of a dissolved bonding agent (an adherent)
which is left after the seam has been completed and cured.  The adherent thus
becomes an additional element in the system.  Contact adhesives are applied to
both mating surfaces.  After reaching the proper degree of tackiness, the two
sheets are placed on top of one another, followed by roller pressure.  The
adhesive forms the bond and is an additional element in the system.

     Other emerging seaming methods use ultrasonic, electrical conduction and
magnetic induction energy sources.  Since these methods are in a development
stage, they are included in a separate section entitled, "Emerging Technologies
for Geomembrane Seaming."

     In order to gain an overview as to which seaming methods are used for the
various thermoplastic geomembranes described in this document, Table 4.2 is
offered.  It is generalized, but it is used to further introduce the six
specific seaming methods to be described in the following sections.
                                       19

-------
TABLE 4.2. MOST COMMONLY USED FIELD SEAMING METHODS FOR VARIOUS  GEOMEMBRANES.
Type of Seaming
    Method
                                       Type of Geomembrane


                    CPE  CPE-R  CSPE-R   EIA  EIA-R  HOPE   PVC   PVC-R  VLDPE
extrusion fillet    n/a    n/a    n/a    n/a    n/a    A    n/a    n/a     A
extrusion flat
hot air
hot wedge
chemical
adhesive
                    n/a    n/a    n/a    n/a    n/a    A    n/a     n/a     A
                                                 A    n/a    A      A    n/a
                                                 A    n/a    A      An/a
Note:    A   =  method is applicable
         n/a =  method is "not applicable"
                                      20

-------
FIELD NOTES:
                                      21

-------
FIELD NOTES:
                                       22

-------
                                  SECTION 5

                      DETAILS OF EXTRUSION FILLET SEAMS


     As seen in Table 4.2, extrusion fillet seaming is an applicable seaming
method for HOPE and VLDPE geomembranes.  In fact, around details such as
pipes and sumps it is always necessary to use a certain amount of extrusion
fillet seaming.  This method is also used for repairs. Thus the text in this
section is written with HOPE and VLDPE geomembranes in mind.


5.1  GEOMEMBRANE PREPARATION

     (a)   Note, that this document assumes that the proper geomembrane has
           been visually inspected to ensure that the sheet is free of deep
           scratches or defects that would cause the sheet to not meet the
           specifications of the installation.  It is further assumed the
           sheet  has been delivered to the site and brought to its
           approximate plan position for final installation and seaming.
           Only the material that can be seamed that day should be deployed.
           All deployed material should be adequately ballasted to prevent
           wind uplift.

     (b)   The geomembrane, HOPE or VLDPE, will usually arrive on site in
           rolls.

     (c)   The geomembrane should remain packaged or rolled and dry until
           ready to use.  The material should not be unrolled if the material
           temperatures are lower than -10C (14F) due to  the  possibility  of
           cracking.  If the panel is stored in a warm place, e.g. 10C
           (50F)  or above,  prior to being unrolled on site,  then it can be
           placed at -18C (0F)  or  below  temperatures providing  the  time
           between removing the geomembrane from storage and deployment does
           not exceed one-half working day.  Geomembrane deployment may be
           allowed under other conditions but the CQC/CQA Documents and/or
           project specifications must be specific as to the conditions.

     (d)   The two geomembrane sheets to be joined must be properly
           positioned such that approximately 7.5 cm to 15.0 cm (3 to 6
           inches) of overlap exists.

     (e)   All personnel walking on the geomembrane should have smooth soled
           shoes.  Heavy equipment,  e.g. pickups, tractors, etc., should not
           be allowed on the geomembrane at any time, unless otherwise
           specified by the manufacturer and approved in the CQC/CQA
           Documents.

                                      23

-------
I
             (f)   If the overlap is insufficient, lift the geomembrane sheet up to
                   allow air beneath it and "float" it into proper position.  Avoid
                   dragging geomembrane sheets made from HOPE particularly when they
                   are on rough soil subgrades since scratches in the material may
                   create stress points of different depths and orientations.

             (g)   If the overlap is excessive and is to be removed,  it should be
                   done by trimming the lower sheet only.  If this is not possible
                   and the upper sheet must be trimmed, do not use a knife with an
                   unshielded blade to cut off the excessive amount because the blade
                   facing downward can easily scratch the underlying geomembrane in a
                   very vulnerable location.  A shielded blade or a hook blade should
                   be used to trim off the excess geomembrane.  A photograph of such
                   a device is shown in Figure 5.1.  Whenever possible it should be
                   used from beneath the liner in an upward cutting motion.
           Figure 5.1.   Type  of hook blade  used  for  the  cutting of  liner materials.


             (h)   All cutting and preparation of odd shaped sections or small fitted
                   pieces should be completed at least 15 m (50 ft.) ahead of the
                   seaming operation so that seaming may be continued with as few
                   interruptions as possible.

             (i)   Visually check the two opposing geomembrane sheets to be joined
                   for defects of sufficient magnitude to affect seam quality.  The
                   criteria to be met and the procedures to be used in this regard
                   should be stipulated in the contract specifications and/or in the
                   CQC/CQA Documents.

                                              24

-------
(j)   If the Construction Plans require overlaps to be shingled in a
      particular direction, this should be checked.

(k)   Excessive undulations (waves) along the seams during the seaming
      operations should be avoided.  When this occurs due to either the
      upper or lower sheet having more slack than the other or because
      of thermal expansion or contraction, it often leads to the
      undesirable formation of "fishmouths" which must be trimmed, laid
      flat and reseamed with a patch.

(1)   There should be some slack in the installed liner,  which depends
      on the type of geomembrane, the ambient and anticipated service
      temperatures, length of time the geomembrane will be exposed,
      location in the facility, etc.  This is a design consideration and
      the Contract Plans and Specifications must be project specific on
      the amount and orientation of slack.

(m)   The sheets which are overlapped for seaming must be clean.  If
      dirty, they must be wiped clean with dry rags or other appropriate
      materials.

(n)   The sheets which are overlapped for seaming must be completely
      free of moisture in the area of the seam.   In the case of
      moisture, air blowers are usually preferred over rags for drying
      the geomembrane.

(o)   Seaming is not allowed during rain or snow, unless  proper
      precautions are made to allow the seam to be made on dry
      geomembrane materials, e.g.,  within an enclosure or shelter.

(p)   It is preferable not to have water-saturated soil beneath the
      geomembrane during installation.  Seaming boards help in this
      regard by lifting the seams off the soil  subgrade.

(q)   If the soil  beneath the geomembrane is frozen,  the  heat of seaming
      can thaw the frost possibly allowing water to condense on the
      unbonded region ahead of the seam being fabricated.   This
      possibility may be eliminated by the use of suitable seaming
      boards or slip sheets made from excess pieces of geomembrane.

(r)   The temperature of the geomembrane for seaming  should be above
      freezing, i.e. O'C, (32F) unless it can be proven  with test
      strips that  good seams can be fabricated at lower temperatures.
      However, temperature is less a concern to  good  seam quality than
      is moisture.

(s)   For cold weather seaming,  it  may be advisable to preheat the
      sheets with  a hot air blower, to use a tent of  some sort to
      prevent heat losses during seaming and to  make  numerous test
      strips in order to determine appropriate seaming conditions, e.g.,
      equipment temperatures may have to be set  higher and seaming rates
      slowed down  during cold weather seaming.

                                25

-------
I
     (t)   Sheet temperatures for seaming should be below 50"C (122F)  as
           measured by an infrared thermometer or surface contact
           thermocouple.   It is recognized that depending on material  type
           and thickness, higher temperatures may be allowed.  It should also
           be recognized  that wind and cloud cover will  determine the  actual
           sheet temperature.  High temperatures affect  not only worker
           performance but will also effect durability of some geomembranes
           unless special precautions, e.g. tents, etc.,  are taken.   For
           temperatures above this value special attention should be paid to
           the seaming operation.  Frequent test strips  and more diligent
           nondestructive testing is recommended.
           NOTE:  For items (q), (r),  (s,) and (t) the CQC/CQA Documents
           and/or project specifications and the regulatory requirements
           regarding hot  and cold temperature seaming limitations should be
           reviewed to avoid possible  problems with final construction
           certification  acceptance.


5.2  EQUIPMENT PREPARATION

     (a)   Properly functioning portable electric generators must be
           available within close proximity of the seaming region and  with
           adequate extension cords to complete the entire seam.  These
           generators should be of sufficient size or numbers to handle all
           seaming electrical requirements. The generator must have  rubber
           tires, or be placed on a smooth plate such that it is completely
           stable so that no damage can occur to the geomembrane or  to  the
           underlying clay liner or subgrade material.  Fuel (gasoline  or
           diesel) for the generator must be stored away from the geomembrane
           and if accidently spilled on the geomembrane  it must be
           immediately removed.  The area should be inspected for damage to
           the geomembrane and repaired if necessary.

     (b)   An electric rotary grinder having a grinding  disk of approximately
           10 cm (4 inch) in diameter and a sufficient quantity of #80  grit
           paper must be  available, see the photograph in Figure 5.2.   Also
           acceptable is  #100 grit paper which is finer  than #80.  Sandpaper
           coarser than #80, e.g. #60, is not acceptable.  Caution should be
           used to prevent overgrinding.


     (c)   A hot air welder with temperature capability  to 250C (475'F)
           must be available to periodically tack weld the geomembrane  sheets
           after they are properly positioned.  The hot  air tacking  should
           not be strong  enough to produce a film tearing bond or interfere
           with the testing of the seam in either peel or shear.
           Occasionally,  double-sided tape is used to temporarily anchor two
           sheets to be seamed. This practice is not recommended unless the
           tape is placed sufficiently far from the seam itself to ensure
           that it will not get to the seam area.
                                             26

-------
      Figure 5.2.  Hand-held electric rotary grinder with
                   circular disc grit grinding paper.


(d)   The extrusion fillet welding apparatus may be of two types,
      depending upon the location where the seams are to be made.
      Either rubber wheeled, automated seam extruders or hand-held
      portable extruders are available.  Photographs of various systems
      are shown in Figure 5.3.

(e)   All extrusion fillet seaming devices must be equipped with
      properly functioning temperature controllers displaying the
      temperature in the extrusion barrel  so that it may be monitored by
      seaming personnel.  It is recommended that the temperature of the
      extrudate be periodically made to check the reading of the
      thermocouple permanently  mounted on  the barrel.  The CQC/CQA
      Documents should be reviewed for appropriate temperature ranges.

(f)   Extrusion fillet seaming  devices have various Teflon or metal  dies
      of different shapes and sizes where  the extrudate exits onto the
      geomembrane.  These dies  must be inspected for wear, sharp notches
      or creases, and for correctness for  the particular application.
      Commercially available extrusion dies are available for most
      common geomembrane thicknesses.  Many, however, are specifically
      made or modified by installers.  Both the width and thickness  of
      the extrudate are dependent upon the proper die.     It should  be
      noted that nozzle selection will vary with geomembrane thickness.
                                27

-------
Figure 5.3.   Photographs of various types of extrusion fillet welding
             devices.
             Upper:   Automated type
             Lower:   Hand-held type
                                  28

-------
     (g)   Adequate extrudate welding rods or pellets, of the same
           composition as the geomembrane itself, must be used.  They must be
           dry, clean and ready for feeding through the extruder.  All
           extrudate resin must be properly formulated so as to be the same
           compound as the geomembrane sheet material.  Manufacturers may be
           required to provide a certification letter indicating that the
           welding rod or pellets and the sheet are the same compound.   If in
           doubt, verification methods must be performed, see Reference  7.
           All extrudate material must be kept dry and free of dirt, debris
           and foreign matter.  When welding rod is used the size must be
           consistent and appropriate for the seaming device.


5.3  TEST STRIPS

     A general requirement of most CQA Documents is that "test seams" or
"test strips" be made on a periodic basis.  Test strips generally reflect the
quality of field seams but should never be used solely for final field seam
acceptance.  Final field seam acceptance should be specified in the contract
specification and should include a minimum level of destructive testing of
the production field seams.  Test strips are made to minimize the amount of
destructive sampling/testing which requires subsequent repair of the final
field seam.  Typically these test seams, for each seaming crew, are made
about every four hours, or every time equipment is changed, or if significant
changes in geomembrane temperature are observed, or as required in the
contract specification.  This is a recommended practice that should be
followed when seaming all types of geomembranes.  The purpose of these tests
is to establish that proper seaming materials, temperatures, pressures,
rates,  and techniques along with the necessary geomembrane pre-seaming
preparation is being accomplished.  Test strips may be used for CQA/CQC
evaluation, archiving, for exposure tests, etc., and must be of sufficient
length to satisfy these various needs.

     Each seaming crew and the materials they are using must be traceable and
identifiable to their test seams.  While the test seams are being prepared,
cured,  and CQC tested, the seaming crew may continue to work as long as the
seams they have made (and are making) since their last acceptable test sample
strip was prepared, are completely traceable and identifiable.   If a test
seam fails to meet the field seam design specification, then an additional
test seam sample will have to be made by the same seaming crew - using the
same tools, equipment and seaming materials - and retested.

     The liner's finished field seams will not be accepted unless the before
and after "test seam sample strip" CQC test results (or other CQC seam test
result  criteria as required per the design specification) are acceptable per
the site's design specifications.  If a seam is not accepted,  destructive
testing of samples from the actual seam will  be removed from the liner and
tested.   If the actual seam destructive test results still  do not meet the
design  specification requirement, then the unacceptable seams will  all  have
to be repaired or reconstructed with seaming materials by a test proven
seaming crew that has passed its testing requirements.  The procedure
illustrated in the flow chart of Figure 5.4 must be followed.   Note that the

                                     29

-------
                      Not*: Sumlng Cnw filling to Pnatn
                       Acctpttblt Tttt Strip* Htyfitquln
                       attaining tiAeconfinct trlth CQC/CQA Documtntt
Figure  5.4.   Test strip  process  flow chart.

                          30

-------
failure of test strip 1 requires two actions:  (a) the making of test strip
2, and (b) an increased frequency of destructive tests on production field
seams made during the curing of test strip 1 (if any were made).  This
increased frequency must be stipulated in the contract specifications or in
the CQC/CQA Documents.

     If the destructive seams fail or if test strip 2 fails, production field
seaming is halted.  All production field seams made during the interval are
repaired per the contract specifications or CQC/CQA Documents to the point of
previous acceptance with an approved seaming crew.

     At this point, the seaming crew that failed to pass both strip tests
must adjust and recertify current seaming equipment and technique or obtain
new seaming equipment, tools and/or retrain personnel and begin making
initial test strip samples.

     Test strips are shown in Figure 5.5(a-e).  Figure 5.5(a) shows a sample
of the geomembrane being cut to form the two pieces to be seamed together.
Figure 5.5(b) shows the hot air tacking of the two pieces together so as to
maintain their respective positions.  Figure 5.5(c) shows the grinding and
beveling of the leading edge for deposition of the extrudate.  Figure 5.5(d)
shows the extrusion fillet seam being placed symmetrically over the edge of
the upper sheet.  Figure 5.5(e) shows the completed test strip cut into three
sections and identified for the parties involved as per the CQC/CQA
Documents.  For geomembranes that are seamed by extrusion or thermal methods
the seams can be tested after they are allowed to cool in ambient air at
least 5 to 10 minutes prior to peel and shear testing.

     As previously stated, all seam test samples must be prepared in
triplicate sets from a single continuous test strip which can be cut into
thirds; one set for CQC tests, one set for CQA tests and one set made
available to (or retained for) the agency/owner/design organization.  If
referee test results are required, CQA test results from destructive testing
of actual seam samples will prevail.

     During the CQC and CQA test evaluation periods, a liner should not be
covered and it cannot be placed into service.  This will insure that it is
available for repairing or reconstructing in the event it is required.
During this period it is imperative that the liner be properly ballasted or
otherwise secured so as to prevent wind or unusual weather damage.


5.4  ACTUAL SEAMING PROCESS

     (a)    Whenever HOPE geomembranes are 1.5 mm (60 mils) in thickness or
           greater, the leading edge of the upper sheet must be ground to a
           45" bevel.  It is important that the sheet to be beveled is lifted
           up off the lower sheet so that no grind marks whatsoever occur in
           the lower sheet outside of the area to be seamed, see Figure 5.6.
           Note that grinding should be done prior to tack welding in order
           to exercise control against damage to the lower sheet.


                                     31

-------

I
           Figure 5.5(a).  A polyethylene geomcmbrane sample being cut into two
                           sections for fabrication of the test strip.

           Figure 5.5(b).  The two sections of geomembrane being hot air "tacked"
                           so as to maintain their proper positioning and preventing
                           movement during seaming.
                                              32

-------
Figure 5.5(c).   Grinding of geomembrane surfaces to remove
                surface oxides and waxes.

Figure 5.5(d).   Placement of extrudate on  the prepared polyethylene
                geomembrane surface.   Movement is from left to right
                in the photograph.
                                 33

-------
 Figure 5.5(e).  The completed  test strip has been cut into three
                 sections and  identified for the parties involved
                 to destructively test or archieve.
        Grinding Wheel
                                             Extreme care must be exercised
                                             so that this surface is not
                                             touched with grinding wheel
                    75  mm  (3 in.) Min.
Figure 5.6.  Preparing the  bevel  of the upper geomembrane for  liner
             thicknesses greater  than 1.5 mm (60 mil.)

                                 34

-------
(b)   Following the preparation of the bevel,  the upper sheet is lowered
      and laid flat on the lower sheet and the horizontal surface
      grinding of both upper and lower sheets  is completed as shown in
      Figure 5.7.  All of the surface sheen in the area to be seamed
      must be totally removed.  Heavy textured grit sand papers coarser
      than #80 size that leaves deep grooves that might become stress
      points or leak channels are unacceptable.   All  of the material
      that has been ground from the geomembrane sheets must be wiped or
      blown away from the actual seaming zone.

^ Extrudate Width ^j
^ To Be C
12-25 mm
^ (0.5 - 1.0 in.) *
*^ 	
Upper Geomembrane """""""'*fy>
Covered
12 - 25 mm
(0.5 - 1.0 in.) *
*r\

                                     f*7////SXS/lW//Ss
                                                  Lower Geomembrane
                    75 mm (3  in.JMin.
  Surfaces To Be
Prepared By Grinding
Figure 5.7.   Proper orientation and grinding preparation of sheets
             prior to tacking and extrudate placement.


(c)   The preferred orientation of grinding marks is perpendicular to
      the seam direction rather than parallel  to it.  It should be
      mentioned that this is a slow process for the installation
      contractor to perform.  The reasoning against parallel grinding is
      that deep, parallel grooves decrease parent material  thickness in
      the direction of stress application across the seam and can lead
      to seam failure in the parent material.   Although the film tearing
      bond criterion is usually satisfied, it is often  at a reduced
      stress due to the thinner material, see Figure 5.8 for the
      distinction between the two different orientation patterns.
      Please note that both grinding patterns in Figure 5.8 are
      excessive and improper in their extent beyond the extrudate and
      are shown for illustration purposes only.

(d)   The depth of the grinding marks (whatever the direction) is of
      paramount interest.  Initial grinding depths should be targeted to
      be less than 5% of the sheet thickness.   Areas where  grinding
      depths are greater than 10% should not be incorporated into the
      seam.   The objective of grinding is to remove oxidized layers and
      waxes  from the geomembrane surfaces and to roughen the seam areas
      of the sheets for bonding to the extrudate.  The  grinding should
      yield  a fine grained smooth surface.  The amount  of material
                                35

-------

Figure 5.8.   Photographs of different orientations of grinding patterns.
             Upper:  Grind marks perpendicular to seams (recommended pattern)
             Lower:  Grind marks parallel  to seam (not recommended pattern)

             (Note,  however,  that  both situations have grinding far in
             excess  of what is  required and are  shown for illustration of
             the grinding patterns only,  see Figure 5.9 following).

                                     36

-------
      removed by grinding  should  be minimal  as  only  a nominal  amount of
      sheeting needs to be removed to achieve a new  surface.   Should
      grind depth exceed 10% of sheet thickness,  then the seam area must
      be adjusted such that improperly ground area is not involved in
      the seam or that improperly ground  area should be physically
      removed.

(e)    Regarding the extent of the grinding,  the general rule  should be
      that grinding marks  should  not appear  beyond 0.6 cm (1/4 inch) of
      the extrudate after  it is placed, see  Figure 5.9.  Thus, if the
      final extrudate bead width  is 4.0 cm (1.5 in.) in width, the total
      grinding pattern should be  no more  than 5.0 cm (2.0 in.),  which is
      equidistant on each  side of the weld centerline.

(f)    Grinding shall be completed no more than  10 minutes before seaming
      takes place so that  oxidized surface layers are not recreated
      prior to placement of the extrudate and to prevent dirt from
      embedding itself in  the patterned grooves.

(g)    The hand held grinder used  for the  grinding process must be turned
      off whenever it is not in use.  Never  leave it running.   If it
      contacts the liner while running it will  cause serious  damage.

(h)    Note that if the temporary tacking  (refer to Section 5.2)  is done
      before the beveling  and grinding operations described in steps (a)
      through (g), then extreme caution against overgrinding  and
      mistakes must be taken.  It might be necessary to provide a wedge
      to lift up the overlying geomembrane as shown  in Figure 5.10, or
      to use a thin metal  sheet with rounded corners and slide it along
      the grinding area on top of the bottom sheet.   If double sided
      tape is used for temporary tacking, it should  be placed far enough
      from the edges to not interfere with the  fusion process.

(i)    The extrusion welder is to  be purged of all aged extrudate in the
      barrel prior to beginning a seam.   This must be done every time
      the extruder is restarted after a 2 min., or longer, period of
      inactivity.  The purged extrudate should  not be discharged onto
      the surface of previously placed liner nor on  the prepared
      subgrade where it would eventually  form a hard lump under the
      liner causing stress concentrations and possibly premature
      failure.

(j)    Extrudate in the form of a molten,  highly viscous fluid is now
      deposited over the overlapped geomembrane.   The center  of the
      extrudate must be located directly  over the edge of the upper
      geomembrane.   The extrudate should cover the  grind marks on each
      side of the upper and lower geomembranes  to within 0.6  cm (1/4
      inch) of the outside borders.
                                37

-------
Figure 5.9.   Photographs of different extent of grinding patterns after
             extrusion fillet seaming.
             Upper:   Excessive and irregular grinding beyond extrudate.
             Lower:   Acceptable grinding pattern just showing beyond
                     extrudate.

                                38

-------
                   Hot Air Tacking
                       Zone
       Upper Geomembrane
       	(8888888S888888
Temporary
Propping
Wedge
                                                     Lower Geomembrane
Figure 5.10.  Smooth propping wedge used when tacking of sheets is done
              before surface grinding of the geomembrane sheets.


  (k)    The extrudate thickness should be approximately equal to or
        greater than the specified sheet thickness measured from the top
        of the upper sheet to the top or crown of the extrudate, see
        Figure 5.11.  Excessive squeeze-out (or flashing) as shown in the
        lower sketch of Figure 5.11 is acceptable as long as it is
        properly joined with the geomembrane, symmetric and will not
        interfere with subsequent vacuum box testing.  If, however,
        pulling up on the extrudate squeeze-out pulls the entire extrudate
        off the sheet it is obviously unacceptable.  Squeeze-out generally
        means that the extrusion die was not riding directly against the
        geomembrane, the extrudate temperature was improper for adequate
        flow, or the seaming rate was too slow.
                                       Extrudate
                                                 Squeeze-Out
                                                 or Flashing
     Figure  5.11.   Schematic diagrams of various cross sections of
                   extrusion fillet seams.
                                  39

-------
     (1)   Where possible,  inspect the underside of the lower geomembrane for
           heat distortion.   This can be done at the end of seams and where
           samples are cut  out of the seam.   If the underside is greatly
           distorted, lower the temperature  or increase the rate of seaming.
           For thick HOPE geomembranes of 2  mm (80 mils) or greater there
           should never be  any indication of this type of thermal
           "puckering".  VLDPE seams which receive too much heat during
           seaming will exhibit an increase  in the amount of waves visible
           along the length of the seam.

     (m)   If properly planned, each seam run should terminate at a panel
           end, at a specific detail or on a long straight run where it can
           be easily resumed.

     (n)   If the seaming needs to be interrupted at mid-seam, the extrudate
           should end abruptly, with the extrudate being no thicker than in a
           normal weld, rather than terminate with a large mass of solidified
           extrudate.

     (o)   Where extrusion  fillet welds are  temporarily terminated long
           enough to cool,  they must be ground prior to applying new
           extrudate over the existing seam.  This restart procedure must
           necessarily be followed on patches, pipes,  fittings, appurtenances
           and "T" or "Y" shaped seams.

     (p)   Depending upon the records to be  kept, one might record a number
           of different temperatures and/or  the rate of seaming.  This is a
           site specific decision usually determined by the contract
           specification or CQC/CQA Documents.
5.5  AFTER SEAMING

     (a)   A smooth insulating plate or heat insulating fabric is always to
           be placed beneath the hot extrusion welding apparatus after usage.
           The tip die and barrel  must not be placed  on any geomembrane or
           other geosynthetic surface - it is extremely hot and can cause
           severe damage.

     (b)   Visual inspection of the extrudate bead should be made
           particularly for straight line alignment,  height, and uniformity
           of surface texture.  There should be no bubbles or pock marks in
           the extrudate.   Such surface details on the extrudate indicates
           the presence of air, water or debris within the extrudate rod or
           pelletized polymer.

     (c)   Grind marks should only be visible for 0.6 cm (1/4 inch) beyond
           the extrudate.   They should be extremely faint and never appear as
           heavy gouge marks, recall Figures 5.8 and  5.9.  Excessive grinding
           also has a depth consideration.  As stated previously, excessive
           is considered to be greater than 10% of the geomembrane thickness.
           If it is excessive, it is not acceptable to apply additional

                                      40

-------
           extrudate over the original extrusion fillet seam.  It is
           necessary to place a cap strip over the entire seam where the
           excessive grinding is observed.

     (d)   The seam must be checked visually for uniformity of width and
           surface continuity.  Usually the installer will use a vacuum box
           to check for voids or gaps in the seam.

     (e)   When unbonded areas are located, they should be patched with at
           least 15 cm (6 inches) of geomembrane extending on all sides.

     (f)   Any area of the geomembrane where puncture holes are observed must
           be patched as above with at least 15 cm (6 inches) of geomembrane
           extending beyond the affected areas.

     (g)   Photographs of various types of extrusion fillet seams follow in
           Figure 5.12.


5.6  UNUSUAL CONDITIONS

     This section is written to give insight into conditions which go beyond
the general description just presented.

     (a)   High winds, or gusts of wind, are always problematic for the liner
           installation process.   After deploying the geomembrane, the panels
           or rolls must be adequately ballasted with sandbags.  The actual
           seam fabrication, however,  will require the removal  of some of the
           sandbags leaving the windward edge vulnerable to wind uplift
           forces.   If possible,  proper orientation of the overlap might be
           helpful.  Otherwise,  additional labor must be on hand to only
           remove sandbags immediately in front of the seaming  operation.
           The liner must be cleaned of any dirt and moisture left behind
           after sandbag removal.  They are then to be replaced behind the
           completed seaming operation.

     (b)   Patches  are necessary at locations where destructive test samples
           are removed or where seams  are shown to fail  nondestructive
           testing.  These patches must extend a minimum of 15  cm (6 inches)
           beyond the outer limits of  the area to be repaired.   For HOPE
           liners the only method available is a hand held extrusion fillet
           procedure as described in this section.   Particular  care must be
           exercised when the end of the extrudate meets the beginning of the
           circumferential  patching run.  The double heat that  the polymer
           will  necessarily experience cannot be excessive,  i.e.,  a large
           mass of  extrudate should not be visible at this location.   For
           VLDPE hot air seaming  can be used to install  patches.

     (c)   Details  around sumps,  pipes and other appurtenances  for HOPE and
           VLDPE liners are generally  made by hand-held  extrusion fillet
           proedures as described in this section.   They are perhaps  the most
           critical seams in a facility.  Also due to their typical

                                     41

-------
Figure 5.12.   Photographs of cross sections of various types of HOPE
              extrusion fillet seams.
              Upper:    Machine extrusion seam without squeeze-out.
              Middle:  Hand held extrusion seam without squeeze-out (note
                       thermal puckering at bottom at seam).
              Lower:    Hand held extrusion seam with squeeze-out.

                                  42

-------
      locations being at low points of the containment facility's
      design,  these areas inherently operate under larger hydraulic
      heads.   Should a defect from improper seaming occur in such a
      location leakage rates and its associated adverse impacts are
      heightened.   Therefore, extreme care should be exercised in
      ensuring seam integrity in these often difficult to reach
      locations.   The extrudate should be symmetric on both sheets to be
      joined  which is difficult for external  and internal edges and
      particularly at corners.   The end of the seam run,  where it joins
      to the  beginning,  should  be a smooth transition and not end with a
      large mass  of extrudate.

(d)    This section was written  for material  temperatures  that range
      between 0C  (32f) and 50C (122F),  which is the temperature
      range that  is generally recognized as being acceptable for seaming
      without taking special  precautions.   For sheet temperatures below
      0C (32F)  , shielding, pre-heating,  and/or a slower seaming rate
      may be  required.  More frequent seam testing and precautions to
      prevent thawing subgrade  may have to be taken.   Sharp, frozen
      subgrade should be avoided to eliminate point pressure damage
      potential.

      For sheet temperatures above 50C (122F),  shielding and rate of
      seaming should be  adjusted.   More frequent destructive seam
      testing may  have to be taken.
                                43

-------
FIELD NOTES:
                                      44

-------
                                   SECTION 6

                        DETAILS OF EXTRUSION FLAT SEAMS


     As seen in Table 4.2, extrusion flat seaming is an applicable method for
the seaming HOPE and VLDPE geomembranes.   Thus, this section is written
primarily for HOPE and VLDPE liners.


6.1  GEOMEMBRANE PREPARATION

     (a)   Note, that this document assumes that the proper geomembrane has
           been visually inspected to ensure it is free of deep scratches, or
           defects that would cause the sheet to not meet the specifications of
           the installation.  It is further assumed the sheet has been
           delivered to the site and brought to its approximate plan position
           for final installation and seaming.  Only the material that can be
           seamed that day should be deployed.  All deployed material should be
           adequately ballasted immediately to prevent wind uplift.

     (b)   The geomembrane, HOPE or VLDPE, will usually arrive on site in
           rolls.

     (c)   The geomembrane should remain packaged or rolled and dry until ready
           to use.  The material should not be unrolled if the material
           temperatures are lower than -10C (14F)  due  to  the  possibility of
           cracking.  If the panel is stored in a warm place, e.g. 10C (50F)
           or above, prior to being unrolled on site, then it can be placed at
           -18C (0F) or  below  temperatures  providing the  time between
           removing the geomembrane from storage and deployment does not exceed
           one-half working day.

     (d)   The two geomembrane sheets to be joined must be properly positioned
           such that approximately 7.5 cm to 15.0 cm (3 to 6 inches) of overlap
           exists.

     (e)   All personnel walking on the geomembrane should have smooth soled
           shoes.  Heavy equipment, e.g.  pickups, tractors, etc., should not be
           allowed on the geomembrane at any time, unless otherwise specified
           by the manufacturer and approved in the CQC/CQA Documents.

     (f)   If the overlap is insufficient, lift the geomembrane sheet up to
           allow air beneath it and "float" it into proper position.  Avoid
           dragging polyethylene geomembrane sheets particularly when they are
           on rough soil subgrades since scratches in the material may create
           various stress points of different depths and orientations.

                                       45

-------
(g)    If the overlap is  excessive and  is  to  be  removed  it  should be done
      by trimming the lower sheet only.   If  this  is  not possible and the
      upper sheet must be  trimmed do not  use a  knife with  an  unshielded
      blade to cut off the excessive amount  because  the blade facing
      downward can easily  scratch the  underlying  geomembrane  in  a very
      vulnerable location.   A shielded blade or a hook  blade  should be
      used to trim off the excess geomembrane.  A photograph  of  such a
      device is shown in Figure  6.1.   Whenever  possible it should be used
      from beneath the liner in  an upward cutting motion.

(h)    All  cutting and preparation of odd  shaped sections or small  fitted
      pieces should be completed at least 15 m  (50 ft.) ahead of the
      seaming operation  so that  seaming may  be  continued with as few
      interruptions as possible.

(i)    Visually check the two opposing  geomembrane sheets to be joined for
      defects of sufficient magnitude  to  affect seam quality.  The
      criteria to be met and the procedures  to  be used  in  this regard
      should be stipulated in the contract specifications  and/or in the
      CQC/CQA Documents.

(j)    If the Plans require overlaps to be shingled in a particular
      direction this should be checked.

(k)    Excessive undulations (waves) along the seams  during the seaming
      operation should be  avoided.  When  this occurs due to either the
      upper or lower sheet having more slack than the other or because of
      thermal expansion  and contraction,  it  often leads to the undesirable
      formation of "fishmouths"  which  must be trimmed,  laid flat and
      reseamed with a patch.

(1)    There should be some slack in the installed liner which depends on
      the type of geomembrane, the ambient and  anticipated service
      temperatures, length of time the geomembrane will be exposed,
      location in the facility,  etc.   This is a design  consideration and
      the Plans and Specifications must be project specific on the amount
      and orientation of slack.

(m)    The sheets which are overlapped  for seaming must  be  clean.  If
      dirty, they must be  wiped  clean  with dry  rags  or  other  appropriate
      materials.

(n)    The sheets which are overlapped  for seaming must  be  completely free
      of moisture in the area of the seam.   In  the case of moisture air
      blowers are usually  preferred over  rags for drying the  membrane.
                                 46

-------
Figure 6.1.  Type of hook blade used in the cutting of liner materials.


 (o)   Seaming is not allowed during rain or snow,  unless proper
       precautions are made to allow the seam to be made on dry geomembrane
       materials, e.g., within an enclosure or shelter.

 (p)   It is preferable not to have water-saturated soil beneath the
       geomembrane during installation.  Seaming boards  help in this regard
       by lifting the seams off the soil subgrade.

 (q)   If the soil beneath the geomembrane is frozen,  the heat of seaming
       can thaw the frost allowing water to be condensed onto the unbonded
       region ahead of the seam being fabricated.   This  possibility may be
       eliminated by the use of suitable seaming boards  or slip sheets made
       from excess pieces of geomembrane.

 (r)   The temperature of the geomembrane for seaming  should be above
       freezing,  i.e. 0C (32F) unless it can be proven with a test strips
       that good  seams can be fabricated at lower temperatures.  However,
       temperature is less a concern to good seam quality than is moisture.

 (s)   For cold weather seaming, it may be advisable to  preheat the sheets
       with a hot air blower, to use a tent of some sort to prevent heat
       losses during seaming and to make numerous test strips in order to
       determine  appropriate seaming conditions, e.g., equipment
       temperatures may have to be set higher and/or seaming rates slowed
       down during cold weather seaming.

                                   47

-------
     (t)   Sheet temperatures for seaming should be below 50C (122F) as
           measured by an infrared thermometer or surface contact thermocopule.
           It is recognized that depending on material  type and thickness,
           higher temperatures may be allowed.  It should also be recognized
           that wind and cloud cover will determine the actual sheet
           temperature.  High temperatures affect not only worker performance
           but will also affect durability of some geomembranes unless special
           precautions, e.g. tents,  etc., are taken.  For temperatures above
           this value special attention should be paid to the seaming
           operation.  Frequent test strips and more diligent nondestructive
           testing is recommended.
           NOTE:  For items (q), (r), (s,) and (t) the CQC/CQA Documents and/or
           project specifications and the regulatory requirements regarding hot
           and cold temperature seaming limitations should be reviewed to avoid
           possible problems with final construction certification acceptance.

6.2  EQUIPMENT PREPARATION

     (a)   Properly functioning portable electric generators must be available
           within close proximity of the seaming region and with adequate
           extension cords to complete the entire seam.  These generators
           should be of sufficient size or numbers to handle all seaming
           electrical requirements.   The generator must have rubber tires, or
           be placed on a smooth plate such that it is completely stable so
           that no damage can occur to the geomembrane or to the underlying
           liner or subgrade material.  Fuel  (gasoline or diesel) for the
           generator must be stored away from the geomembrane and if accidently
           spilled on the geomembrane must be immediately removed.  The area
           should be inspected for damage to the geomembrane and repaired if
           necessary.

     (b)   An electric rotary grinder having a grinding disk of approximately
           10 cm (4 inch) in diameter and a sufficient quantity of #80 grit
           paper must be available.   Also acceptable is #100 grit paper which
           is finer than #80.  Sandpaper coarser than #80, e.g. #60, is not
           acceptable.  Grinding locations are shown in Figure 6.2.  Caution
           should be used to prevent overgrinding.

     (c)   Pressure rollers should be inspected for sharp edges or irregular
           surfaces.  On some systems these rollers are in tandem where the
           front set (nearest the extrudate)  should be adjusted to a lower
           pressure than the rear set.

     (d)   All extrusion flat seaming devices must be equipped with properly
           functioning temperature controllers displaying the temperature in
           the extrusion barrel so that it may be monitored by seaming
           personnel.  It is recommended that the temperature of the extrudate
           with an external thermocouple inserted into the melt stream be
           periodically made to check the reading of the thermocouple
           permanently mounted on the barrel.  The CQC/CQA Documents should be
           reviewed for appropriate temperature ranges.


                                       48

-------
                        Grinding Areas
                   typ. 50 mm (2 in.)

           ROTARY GRINDER
                                                                 Grinding
                                                                 Area
     typ. 50 mm (2 in.)

WIRE BRUSHING
          Figure 6.2.  Grinding locations and method used in the
                       preparation of extrusion flat seams.
     (e)   Adequate extrudate welding rods or pellets of appropriate dimension,
           and of the same composition as the geomembrane itself, must be used.
           They must be dry and clean to feed through the extruder.  All
           extrudate resin must be properly formulated so as to be the same
           compound as the geomembrane sheet material.  Manufacturers may be
           required to provide a certification letter indicating that the
           welding rod or pellets and the sheet are the same compound. If in
           doubt, chemical fingerprinting methods must be performed, see
           Reference 7.  All extrudate material must be kept dry and free of
           dirt, debris and foreign matter.  When welding rod is used the size
           must be consistent and appropriate for the seaming device.


6.3  TEST STRIPS

     A general requirement of most CQA Documents is that "test seams" or "test
strips" be made on a periodic basis.  Test strips generally reflect the quality
of field seams but should never be used solely for final field seam acceptance.
Final field seam acceptance should be specified in the contract specification
and should include a minimum level of destructive testing of the production
field seams.  Test strips are made to minimize the amount of destructive
sampling/testing which requires subsequent repair of the final field seam.
Typically these test seams, for each seaming crew, are made about every four
hours,  or every time equipment is changed, or if significant changes in
geomembrane temperature are observed, or as required in the contract
specification.  This is a recommended practice that should be followed when
seaming all types of geomembranes.  The purpose of these tests is to establish
that proper seaming materials, temperatures, pressures,  rates, and techniques
along with the necessary geomembrane pre-seaming preparation is being
accomplished.  Test strips may be used for CQA/CQC evaluation, archiving, for
exposure tests, etc.,  and must be of sufficient length to satisfy these various
needs.
                                      49

-------
     Each seaming crew and the materials they are using must be traceable and
identifiable to their test seams.  While the test seams are being prepared,
cured, and CQC tested, the seaming crew may continue to work as long as the
seams they have made (and are making) since their last acceptable test sample
strip was prepared, are completely traceable and identifiable.  If a test seam
fails to meet the field seam design specification, then an additional test seam
sample will have to be made by the same seaming crew - using the same tools,
equipment and seaming materials - and retested.

     The liner's finished field seams will not be accepted unless the before
and after "test seam sample strip" CQC test results (or other CQC seam test
result criteria as required per the design specification) are acceptable per
the site's design specifications.  If a seam is not accepted, destructive
testing of samples from the actual seam will be removed from the liner and
tested.  If the actual seam destructive test results still do not meet the
design specification requirement, then the unacceptable seams will all have to
be repaired or reconstructed with seaming materials by a test proven seaming
crew that has passed its testing requirements.  The procedure illustrated in
the flow chart of Figure 6.3 must be followed.  Note that the failure of test
strip 1 requires two actions:  (a) the making of test strip 2, and (b) an
increased frequency of destructive tests on production field seams made during
the curing of test strip 1 (if any were made).  This increased frequency must
be stipulated in the contract specifications or in the CQC/CQA Documents.

     If the destructive seams fail or if test strip 2 fails, production field
seaming is halted.  All production field seams made during the interval are
repaired per the contract specifications or CQC/CQA Documents to the point of
previous acceptance with an approved seaming crew.

     At this point, the seaming crew that failed to pass both strip tests must
adjust and recertify current seaming equipment and technique or obtain new
seaming equipment, tools and/or retrain personnel  and begin making initial test
strip samples.

     Test strips are prepared as shown in Figure 6.4.  Figure 6.4(a) shows the
flat extrusion device from a side view and Figure 6.4(b) from a rear view.  The
test strips are made on small sections of excess geomembrane in the identical
manner of making actual production seams.  When they cool, they are cut into
sections and properly identified.  For geomembranes that are seamed by
extrusion or thermal methods, the seams can be tested after they are allowed to
cool in ambient air at least 5-10 minutes prior to peel and shear testing.
                                       50

-------
                       Halt: Sttmlng Cnw filling la Pnptrt
                        Aeetpttalt Tttt Strlpt Mty Hta.uln
                        attn/nlng InAeeonltnet wtth CQC/CO4 Documtntt
Figure  6.3.   Test  strip process flow  chart.
                          51

-------
Figure 6.4(a).   Side view of an extrusion flat welding device showing
                the extrudate feed arm between the overlapping
                geomembrane sheets and the roller immediately behind.
                                    52

-------
Figure 6.4(b).   Rear view of the extrusion flat device as it
                would appear at the completion of the seam.

                               53

-------
     As previously stated, all  seam test samples must be prepared in triplicate
sets from a single continuous test strip which can be cut in thirds; one set
for CQC tests, one set for CQA tests and one set made available to (or retained
for) the agency/owner/design organization.   If referee test results are
required, CQA test results from destructive testing of actual  seam samples will
prevail.

     During the CQC and CQA test requirement periods, a liner should not be
covered and it cannot be placed into service.   This will insure repairing or
reconstructing in the event it is required.  During this period it is
imperative that the liner be properly ballasted and otherwise secured so as to
prevent wind or unusual weather damage.


6.4   ACTUAL SEAMING PROCESS

     (a)   Either by surface grinding, preheating air or preheating wedge, the
           area to be seamed should now be ready to accept the extrudate in the
           form of a ribbon placed between the two sheets.

     (b)   If grinding is required, the grinding of the lower sheet is to be
           done first, with a suitable width (approximately 5.0 to 7.5 cm [2 to
           3 inches]) being prepared such that surface oxide is removed and the
           sheet is roughened.   The depth of the grind marks must be no greater
           than 10% of the original thickness  of the sheet.  Initial grinding
           depths should be targeted to be less than 5% of the sheet thickness.
           Areas where grinding depths are greater than 10% should not be
           incorporated into the seam.

     (c)   The upper sheet is bent over backwards but not creased, so that its
           underside can be ground at the location where it will meet the lower
           sheet's prepared surface.  It is important to note that all ground
           sheet must eventually be covered with extrudate to within 0.6 cm
           (1/4 inch).

     (d)   Alternatively to the type of surface preparation just described in
           parts (b), and (d),  an automated wire brush technique can be used.
           With this instrument it is possible to prepare the bottom of the top
           sheet and the top of the bottom sheet at the same time, see Figure
           6.2.  It should be noted that an even surface must be prepared.  The
           surfaces should be inspected for uniformity and grinding depths less
           than or equal to 10% of the sheet thickness.

     (e)   If the flat extrusion device is equipped with pre-heating air or
           pre-heating wedge preceding the extrudate, grinding of either type
           just described is not necessary.  It must be shown, however, by the
           use of test strips that these techniques do, indeed, provide
           adequate seam strength in shear and in peel testing.
                                       54

-------
(f)   Preheating of the opposing surfaces with hot air or hot wedge
      devices must be applied to the full seam width at a constant
      temperature.  The nozzle, or wedge, should be inspected for
      obstructions or scratches on a daily basis.   Care should be taken in
      choosing the nozzle design and magnitude of the air pressure.  If
      excessive air is discharged under the top geomembrane it could
      create a backpressure that may blow dust and small  soil particles
      into the seam area.

(g)   The extrusion welder is to be purged of all  heat-degraded extrudate
      in the barrel prior to beginning a seam.  This must be done every
      time the extruder is restarted after a 2 min., or longer, period of
      inactivity.  The purged extrudate should not be discharged onto the
      surface of previously placed liner nor on the prepared subgrade
      where it would eventually form a hard lump under the liner causing
      stress concentrations and possibly premature failure.

(h)   Some extrudate should also be ejected to see if the nozzle is the
      appropriate width and thickness.  Usually flat extrudate ribbons are
      3.8 to 5.0 cm (1.5 in. to 2.0 in.) wide and  about 1.5 mm (60 mils)
      thick.  However, welding speed will affect this thickness, which
      ranges from about 0.5 mm (20 mils) thick when moving rapidly, to 2.0
      mm (80 mils) thick when moving slowly.  Properly functioning
      temperature controllers must display the extrudate  temperature.  A
      photograph and schematic diagram of a extrusion flat seaming device
      is given in Figure 6.5.

(i)   The extrudate is placed at about (250'C) 480*F in a full width, full
      thickness ribbon, see Figure 6.6.  It cannot be visually inspected
      since it is occurring between the two sheets, directly following the
      sheet preparation by grinding, preheating air or preheating wedge
      and directly preceding the pressure rollers.

(j)   The outside edge of the seam should be visually observed to ensure
      that the extrudate is embedded between the liner sheets.  Three
      cases are possible.  These are:   1) the edge of the extrudate being
      somewhat under the overlapping sheet,  2) exactly even with it, or
      3) beyond it in the form of "squeeze-out".  Either  one of the latter
      two situations are necessary if vacuum box testing  of the seam is
      subsequently required.

(k)   The rollers exert considerable pressure and  are adjusted according
      to sheet thickness.  Indentations on the surface of the upper
      geomembrane should be observable but should  not create a rut, e.g.,
      the indentation should be barely capable of  being felt.
                                 55

-------
I
                                                _We|dinj Direction^
                                             Contoct        HOPE
                                            j Pressure  Extrudate TubeM)ie
                                                      With Hot Air Jets
                                       Principles of Extrusion Welding For Site Joining
                  Figure 6.5.   Photographs  and  schematic  diagram  of extrusion flat
                                  seaming of geomembrane sheets.
                                                     56

-------
                                            Extrudate
             T
typ

k-*

-^ .
. 25 mm tyP- 50 mm
1 in.) (2 in.)
Lower Geomembrane

S 3t
     Figure 6.6.  Schematic diagram of cross section of extrusion flat
                  seam with extrudate out to the edge of the upper
                  geomembrane.
     (1)   Thermal "puckering" of the upper surface of the overlying
           geomembrane should not appear.  Although the lower surface of the
           underlying geomembrane is rarely able to be inspected (except at
           sheet ends, trial strips, or where samples are taken) it should not
           be puckered.  Thermal puckering signifies excessive heat and/or
           insufficient seaming rate.

     (m)   Depending upon the records to be kept, one might record a number of
           different temperatures and/or the rate of seaming.  This is a site
           specific decision usually determined by the contract specification
           or CQC/CQA Documents.

     (n)   It is necessary that the operator keep constant visual contact with
           the temperature controls, as well as the completed seam coming out
           of the machine.  Occasional adjustments of temperature or speed as
           the result of changing ambient conditions will be necessary to
           maintain a consistent seam.  Constant visual and hands on inspection
           is also recommended.  If changes in the welding conditions are made
           as a response to a changing welding environment, an additional
           destructive sample test should be performed shortly after the change
           is made.
6.5  AFTER SEAMING

     (a)   Hand-held grinders or mechanical wire brushes are always to be
           turned off when not in use.  If placed on the geomembrane while
           running, they can cause considerable damage.

     (b)   A smooth insulating plate or heat insulating fabric is to be placed
           beneath any hot welding apparatus after usage.

                                       57

-------
I
     (c)   Grinding marks on the lower sheet of the completed seam should be
           observable but only for a distance of 0.6 cm (1/4 inch) beyond the
           extrudate.  Note, however,  that only the lower sheet can be
           inspected in this regard.

     (d)   If properly planned, each seam run should terminate at a panel end,
           specific detail or on a long straight run where it can be easily
           resumed.

     (e)   Where extrusion flat welds are terminated long enough to cool, the
           start-up continuation seam must completely melt the leading edge of
           the cooled seam.   Since this is occurring beneath the overlapped
           sheet and cannot be observed, the location must be marked for
           subsequent vacuum box testing.  If it fails, the area must be
           repaired or reconstructed.

     (f)   The extrudate end should trail off gradually, rather than terminate
           with a large mass of solidified extrudate.

     (g)   The seam must be checked visually for uniformity of width and
           surface continuity.  Usually the installer will use a vacuum box to
           check for voids or gaps in the seam.

     (h)   When unbonded areas are located, they should be patched with at
           least 15 cm (6 inches) of geomembrane extending on all sides.  Any
           area of the geomembrane where puncture holes are observed must be
           patched as above with at least 15 cm (6 inches) of geomembrane
           extending beyond the affected areas. If grinding is to be performed
           to prepare the geomembrane, review instructions provided in Section
           5.

     (i)   Photographs of the various types of extrusion flat seams are shown
           in Figure 6.7.


6.6  UNUSUAL CONDITIONS

     This section is written to give insight into conditions which go beyond
the general description just presented.

     (a)   High winds, or gusts of wind, are always problematic for liners.
           After deploying the geomembrane, the panels must be adequately
           ballasted with sandbags.  The actual seam fabrication, however, will
           require the removal of some of the sandbags leaving the windward
           edge vulnerable to wind uplift forces.  If possible, proper
           orientation of the overlap might be helpful.  Otherwise, additional
           labor must be on hand to only remove sandbags immediately in front
           of the seaming operation.  The liner must be cleaned of any dirt and
           moisture left behind after sandbag removal.  They are then to be
           replaced behind the completed seaming operation.
                                             58

-------
Figure 6.7.  Photographs of cross sections of HOPE extrusion flat
             seams.
             Upper:   Extrudate short of edge of overlapping sheet.
             Middle:  Extrudate exactly at the edge- of overlapping
                      sheet.
             Lower:   Extrudate squeeze-out beyond the edge of
                      overlapping sheet-.

                                  59

-------
(b)   Patches are necessary at locations where destructive test samples
      are removed or where seams are shown to fail  nondestructive testing.
      These patches must extend a minimum of 15 cm (6 inches)  beyond the
      outer limits of the area to be repaired.  For HOPE liners the only
      method available is a hand held extrusion fillet procedure as
      described in Section 5.   Particular care must be exercised when the
      end of the extrudate meets the beginning of the run.  The double
      heat that the polymer will necessarily experience cannot be
      excessive, i.e., a large mass of extrudate should not be visible at
      this location.

(c)   Details around sumps, pipes and other appurtenances for  HOPE and
      VLDPE liners must necessarily be made by hand-held extrusion fillet
      procedures as described  in Section 5.  They are perhaps  the most
      demanding seams in a facility.  Also due to their typical locations
      being at low points of the containment facility's design, these
      areas inherently operate under larger hydraulic heads.   Should a
      defect from improper seaming occur in such a location leakage rates
      and its associated adverse impacts are heightened.  Therefore,
      extreme care should be exercised in ensuring seam integrity in these
      often difficult to reach locations.  The extrudate should be
      symmetrical on both sheets to be joined which is difficult for
      external and internal edges and particularly at corners.  The end of
      the seam run, where it joins to the beginning,  should be a smooth
      transition and not end with a large mass of extrudate.

(d)   This section was written for material temperatures that  range
      between (0C) 32F and (50C) 122F.  This is the temperature range
      that is generally recognized as being acceptable for seaming without
      taking special precautions.

      For sheet temperatures below 0C (32"F), shielding, preheating,
      and/or a slower seaming  rate may be required.  More frequent seam
      testing and precautions  to prevent thawing subgrade (previously
      discussed) may have to be taken.  Sharp, frozen subgrade should be
      avoided to eliminate point pressure damage potential.

      For sheet temperatures above 50'C (122F), shielding and rate of
      seaming should be adjusted.  More frequent destructive seam testing
      may have to be taken.
                                 60

-------
FIELD NOTES:
                                       61

-------
       FIELD  NOTES:
I
                                              62

-------
                                 SECTION 7

                         DETAILS OF HOT WEDGE SEAMS
     As seen in Table 4.2,  hot wedge seaming is an applicable method for the
seaming all  thermoplastic geomembranes.


7.1  GEOMEMBRANE PREPARATION

     (a)   Note, that this document assumes that the proper geomembrane has
           been visually inspected to ensure it is free of deep scratches,
           or defects that would cause the sheet to not meet the
           specifications of the installation.   It is further assumed the
           sheet has been delivered to the site and brought to its
           approximate plan position for final  installation and seaming.
           Only the material that can be seamed that day should be deployed.
           All  deployed material should  be ballasted as required to prevent
           wind uplift.

     (b)   If the geomembrane is CPE, CPE-R, CSPE-R, EIA,  EIA-R, PVC or
           PVC-R it will usually arrive  on site in the form of fabricated
           panels which are accordion-folded in both directions.  They are
           generally packaged in palletized, heavy cardboard containers.   If
           the  geomembrane is HOPE or VLDPE, it will arrive on the site in
           rolls.

     (c)   The  geomembrane should remain packaged or rolled and dry until
           ready to use.  The material  should not be unfolded or unrolled if
           the  material temperatures are lower than -10"C  (14"F) due to the
           possibility of cracking.  If  the panel  is stored in a warm place,
           e.g. 10C (50'F) or above, prior to being unfolded or unrolled on
           site, then it can be placed at -18'C (O'F) or below temperatures
           providing the time between removing the geomembrane from storage
           and  deployment does not exceed one-half working day.   Geomembrane
           deployment may be allowed under other conditions but the CQC/CQA
           Documents and/or project specifications must be specific as to
           the  conditions.

     (d)   The  two geomembrane sheets to be joined must be properly
           positioned such  that approximately 7.5 cm to 15.0 cm (3 to 6
           inches) of overlap exists. All  personnel walking on the
           geomembrane should have smooth soled shoes.   Heavy equipment,
           e.g. pickups, tractors,  etc., should not be allowed on the
           geomembrane at any time, unless otherwise specified by the
           manufacturer and approved in  the CQC/CQA Documents.

                                     63

-------
(e)    If the overlap is insufficient and it  does  not fully cover the
      wedge, lift the geomembrane up to allow air beneath  it and
      "float" it into proper position.   Avoid dragging  geomembrane
      sheets made from HOPE particularly when they are  on  rough soil
      subgrades since scratches in the  material create  stress points of
      different depths and orientations.

(f)    When most reinforced geomembranes are  cut to accommodate odd
      shapes or to fit small  pieces, resealing of the exposed scrim by
      flood coating is required by the  use of the manufacturer's or
      fabricator's approved liquid sealant.

(g)    If the overlap is excessive when  placing HOPE and VLDPE and is to
      be removed, it should be done by  trimming the lower  sheet.  If
      this is not possible and the upper sheet must be  trimmed, do not
      use a knife with an unshielded blade to cut off the  excessive
      amount because the blade facing downward can easily  scratch the
      underlying geomembrane in a very  vulnerable location.   A shielded
      blade or a hook blade should be used to trim off  the excess
      geomembrane.  A photograph of such a device is shown in Figure
      7.1.  Whenever possible it should be used from beneath the liner
      in an upward cutting motion.  For liners made from CPE, CPE-R,
      CSPE-R, EIA, EIA-R, PVC, PVC-R and VLDPE the excess  material can
      be cut by a scissor or can be worked away from the edges of the
      seam to maintain proper overlap.

(h)    All cutting and preparation of odd shaped sections or small
      fitted pieces should be completed at least  15 m (50  ft.) ahead of
      the seaming operation so that seaming  can be completed with as
      few interruptions as possible.

(i)    The two opposing sheets to be joined should be visually checked
      for defects of sufficient magnitude to affect seam quality.  The
      criteria to be met and the procedures  to be used  in  this regard
      should be stipulated in the contract specifications  and/or in the
      CQC/CQA Documents.

(j)    If the construction plans require overlaps  to be  shingled in a
      particular direction this should  be checked.

(k)    Excessive undulations (waves) along the seams during the seaming
      operation should be avoided.  When this occurs due to either the
      upper or lower sheet having more  slack than the other or because
      of thermal expansion and contraction,  it often leads to the
      undesirable formation of "fishmouths"  which must  be  trimmed, laid
      flat and reseamed with a patch.
                                64

-------
Figure 7.1.   Type of hook blade used in the  cutting  of liner materials.
   (1)   For all liners, there should be some slack in the installed liner
        which depends on the type of geomembrane, ambient and anticipated
        service temperatures, length of time the geomembrane will be
        exposed, location in the facility, etc.  This is a design
        consideration and the Plans and Specifications must be project
        specific on the amount and orientation of slack.

   (m)   The sheets which are overlapped for seaming must be clean.  If
        dirty, they must be cleaned with dry rags or other appropriate
        materials.

   (n)   The sheets which are overlapped for seaming must be free of
        moisture in the area of the seam.

   (o)   Seaming is not allowed during rain or snow, unless proper
        precautions are made to allow the seam to be made with dry
        geomembrane materials, e.g., within an enclosure or shelter.

   (p)   It is preferable not to have water saturated soil beneath the
        geomembrane during installation.  Seaming boards help in this
        regard by lifting the seams off the soil subgrade.

   (q)   If the soil beneath the geomembrane is frozen, the heat from hot
        air seaming devices or any preheating lamps that may be used can
        thaw the frost allowing water to be condensed onto the unbonded

                                  65

-------
           region ahead of the seam being fabricated.   This possibility may
           be eliminated by the use of suitable seaming boards or slip
           sheets made of excess geomembrane material.

     (r)   Ambient temperatures for seaming should be  above freezing,  i.e.,
           0*C (32*F) unless it can be proven with test strips that good
           seams can be fabricated at lower temperatures.   However,
           temperature is less a concern to good seam  quality than is
           moisture.

     (s)   For cold weather seaming,  it may be advisable to preheat the
           sheets with a radiant heater or a blower, to use a tent of  some
           sort to prevent heat losses during seaming  and to make numerous
           test strips in order to determine appropriate seaming conditions,
           e.g., equipment temperatures may have to be set higher and/or
           seaming rates slowed down during cold weather seaming.

     (t)   Sheet temperatures for seaming should be below 50'C (122*F) as
           measured by an infrared thermometer or surface contact
           thermocouple.  It is recognized that depending on material  type
           and thickness, higher temperatures may be allowed.  It should
           also be recognized that wind and cloud cover will determine the
           actual sheet temperature.   High temperatures affect not only
           worker performance but may also affect seam durability of some
           geomembranes unless special precautions are taken.  For
           temperatures above this value, frequent test strips and more
           diligent nondestructive testing is recommended.
           NOTE:  For items (q), (r), (s,) and (t) the CQC/CQA Documents
           and/or project specifications and the regulatory requirements
           regarding hot and cold temperature seaming  limitations should be
           reviewed to avoid possible problems with final  construction
           certification acceptance.


7.2  EQUIPMENT PREPARATION

     (a)   Properly functioning portable electric generators must be
           available within close proximity of the seaming region and  with
           adequate extension cords to complete the entire seam.  These
           generators should be of sufficient size or  numbers to handle all
           seaming electrical requirements.  The generator must have rubber
           tires, or be placed on a smooth plate such  that it is completely
           stable so that it cannot damage the geomembrane or to the
           underlying clay liner or subgrade material.   Fuel (gasoline or
           diesel) for the generator must be stored away from the
           geomembrane, and if accidently spilled on the geomembrane it must
           be immediately removed.  The areas should be inspected for  damage
           to the geomembrane and repaired if necessary.
                                     66

-------
(b)   Hot wedge seaming devices are completely self contained systems
      sometimes referred to as a "mouse" or "hot shoe".   Photographs of
      different types of hot wedge seaming devices are shown in
      Figure 7.2.

(c)   As the hot wedge method is one of melting the opposing surfaces
      of the two sheets to be joined,  no grinding of sheets is
      necessary, nor allowed.

(d)   Hot air tacking of the geomembrane sheets as done  in extrusion
      fillet seaming is not possible since the wedge must travel
      between opposing parallel sheets which are to be joined.

(e)   The hot wedge itself, or "anvil", should be inspected to see that
      it is uniform and uniformly tapered.  Various typ^s are currently
      available.  Some are smooth surfaced while others  have patterned
      ridges in the direction of the seam or at a slight angle.  The
      taper dimensions vary according  to different types of machines.
      The major point for inspection is that no sharp edges should
      exist wherever the wedge meets geomembrane sheet surfaces.

(f)   A single hot wedge has an anvil  which is uniform over its entire
      surface.  A dual wedge has a split anvil forming two separate
      tracks, see the sketches of Figure 7.3.   If a dual, or split, hot
      wedge seam is being made, the recessed space for the central
      unseamed portion should be examined to ensure the  cavity is
      clean.

(g)   Knurled rollers are used for applying pressure on  the sheets and
      driving the device.  They immediately follow the pointed end of
      the anvil.  The knurled rollers  should be inspected to ensure
      there are no sharp surfaces and  that wheels are smoothly beveled
      on the edges.

(h)   If a chain drive powers the device and applies pressure to  the
      nip/drive rollers it should be inspected for synchronization of
      travel, proper functioning and fit.   Loose chains  or damaged
      sprockets should be repaired or  replaced.

(i)   As the geomembrane sheet materials pass  through the machine,  they
      must come in contact with the full width of the wedge in order to
      heat the material  uniformly.   Idler rollers or similar devices,
      on both sides of the wedge are adjustable and must make the
      material  conform to the wedge as it passes through the machine.
      The procedure for doing this with some equipment is as follows:
      Insert the lower and upper layers of geomembrane material  in  the
      nip/drive rollers,  which will  change the wedge height between the
      idler rollers.   Then,  lock the wedge in  position,  and adjust  the
      idlers so that  one layer fits snugly between the wedge and  the
      idlers.   The wedge has an adjustment that is actually a stopping
      device to keep  the wedge from being  pulled into the nip/drive
      rollers.   Caution must be taken  to ensure  that the wedge is not

                                67

-------
Figure 7.2.  Various types of hot wedge seaming devices.
                           68

-------
 typ.  tl
25 mm
(1  in.)
            typ. 75 mm (3 in.) I

              Single Hot Wedge
typ. 25-75 mm
   (1-3  in.)
                                                    typ. 75 mm (3 in.)
                                                  Dual (Split)  Hot Wedge

        Figure  7.3.   Diagrams  of the hot wedge elements  (i.e., the anvil)
                     upon which the two sheets to  be joined are passed.
             adjusted  too  closely to the nip/drive rollers, especially when
             material  is not going through the machine.  The drive, or wedge
             units, must be disengaged before the material runs completely out
             of the machine.   Serious damage will occur to the geomembrane
             sheets if the wedge gets pulled through the nip/drive rollers.

             Please note that  there are automatically adjusting machines  in
             use.  These machines automatically adjust the position of the
             geomembrane with  respect to the roller drive mechanism.  For this
             reason the above  and remaining instructions should be
             appropriately modified.

       (j)    The front part of the seaming device should be inspected for
             sharp corners and irregular details which may damage the
             geomembranes.

       (k)    Temperature controllers on the wedge device should be set
             according to  type of geomembrane, thickness, ambient temperature,
             rate of seaming,  and location of thermocouple within the device.
             Temperature gages should be checked for accuracy and
             repeatability.  Table 7.1 gives typical values but this is a
             site, material and device specific decision usually determined by
             CQC/CQA Documents or site specific conditions.

       (1)    If available, the force sensors at the nip rollers should be
             checked for accuracy and repeatability.
                                      69

-------
     TABLE 7.1.  TEMPERATURE RANGES FOR HOT WEDGE SEAMING OF THERMOPLASTIC
                GEOMEMBRANES (TEMPERATURES ARE WITHIN THE WEDGE ITSELF).
Geomembrane Type
CPE
CPE-R
CSPE-R
EIA
EIA-R
HOPE***
PVC
PVC-R
VLDPE***
Minimum *
C CF)
170 (340)
170 (340)
180 (360)
155 (310)
155 (310)
315 (600)
165 (330)
165 (330)
270 (520)
Maximum **
*C CF)
370 (700)
370 (700)
370 (700)
175 (345)
175 (345)
455 (850)
370 (700)
370 (700)
400 (750)
*    For dry, warm weather seaming conditions
**   For damp, cold weather seaming conditions
***  For textured or roughened HOPE or VLDPE sheet increase temperatures
      about 25'C (45F).  Also slower seaming rates and higher pressures
      may be required.
                                     70

-------
7.3  TEST STRIPS

     A general requirement of most CQA Documents is that "test seams" or
"test strips" be made on a periodic basis.  Test strips generally reflect
the quality of field seams but should never be used solely for final field
seam acceptance.  Final field seam acceptance should be specified in the
contract specification and should include a minimum level of destructive
testing of the production field seams.  Test strips are made to minimize the
amount of destructive sampling/testing which requires subsequent repair of
the final field seam.  Typically these test seams, for each seaming crew,
are made about every four hours, or every time equipment is changed, or if
significant changes in geomembrane temperature are observed or, as required
in the contract specification.  This is a recommended practice that should
be followed when seaming all types of geomembranes.  The purpose of these
tests is to establish that proper seaming materials, temperatures,
pressures, rates, and techniques along with the necessary geomembrane
pre-seaming preparation is being accomplished.  Test strips may be used for
CQA/CQC evaluation, archiving, for exposure tests, etc., and must be of
sufficient length to satisfy these various needs.

     Each seaming crew and the materials they are using must be traceable
and identifiable to their test seams.  While the test seams are being
prepared, cured, and CQC tested, the seaming crew may continue to work as
long as the seams they have made (and are making) since their last
acceptable test sample strip was prepared, are completely traceable and
identifiable.  If a test seam fails to meet the field seam design
specification, then an additional test seam sample will have to be made by
the same seaming crew - using the same tools, equipment and seaming
materials - and retested.

     The liner's finished field seams will not be accepted unless the before
and after "test seam sample strip" CQC test results (or other CQC seam test
result criteria as required per the design specification) are acceptable per
the site's design specifications.  If a seam is not accepted, destructive
testing of samples from the actual seam will be removed from the liner and
tested.  If the actual seam destructive test results still  do not meet the
design specification requirement, then the unacceptable seams will all have
to be repaired or reconstructed with seaming materials by a test proven
seaming crew that has passed its testing requirements.  The procedure
illustrated in the flow chart of Figure 7.4 must be followed.  Note that the
failure of test strip 1 requires two actions:  (a) the making of test strip
2, and (b) an increased frequency of destructive tests on production field
seams made during the curing of test strip 1 (if any were made).  This
increased frequency must be stipulated in the contract specifications or in
the CQC/CQA Documents.

     If the destructive seams fail or if test strip 2 fails,  production
field seaming is halted.  All production field seams made during the
interval  are repaired per the contract specifications or CQC/CQA Documents
to the point of previous acceptance with an approved seaming crew.
                                     71

-------
                       Holt: Sttmlng Cnw filling to frt/m
                        Acctpttblt Tttt Stript MtyRtquIn
                        RttrtlnlnglnAccanitnct HH/I CQC/COA Deamntt
Figure  7.4.   Test  strip process flow  chart.

                          72

-------
     At this point, the seaming crew that failed to pass both strip tests
must adjust and recertify current seaming equipment and technique or obtain
new seaming equipment, tools and/or retrain personnel and begin making
initial test strip samples.

     For hot wedge seams test strips of the type shown in Figure 7.5(a-d)
are prepared.  The seam is centered lengthwise between the two sheets to be
joined.  Figure 7.5(a) shows the two geomembrane pieces to be seamed being
cleaned and properly aligned, 7.5(b) shows the actual test strip being
seamed, 7.5(c) shows the sampling of the test strip for subsequent
destructive testing, and 7.5(d) shows the individual samples cut from the
test strip being identified.  For geomembranes that are seamed by thermal
methods, the seams can be tested after they are allowed to cool in ambient
air at least 5-10 minutes prior to shear and pael testing.

     As previously stated, all seam test samples must be prepared in
triplicate sets preferably in a continuous seam which can be cut in thirds;
one set for CQC tests, one set for CQA tests and one set made available to
(or retained for) the agency/owner/design organization.  If referee test
results are required, CQA test results from destructive tasting of actual
seam samples will prevail.

     During the CQC and CQA test requirement periods, a liner should not be
covered and it cannot be placed into service.   This will insure the ease and
viability of repairing or reconstructing in the event it is required.
During this period it is imperative that the liner be properly ballasted and
otherwise secured so as to prevent wind or unusual  weather damage.


7.4  ACTUAL SEAMING PROCESS

     (a)   The hot wedge system (i.e., the "mouse"  or "hot shoe") should be
           properly positioned for the making  of the desired single or dual
           (split) seam.

     (b)   The principle of the hot wedge is that both surfaces to be  joined
           come into intimate contact with the hot  wedge,  or anvil.   The
           anvil  slides between both layers of geomembranes and fusion is
           brought about by compressing the two melted surfaces together,
           causing an intermingling of the polymers from both sheets.   The
           hot anvil  itself melts the surface  of the viscous polymer sheets
           and acts as a scraper/mixer, followed closely by the nip rollers
           which  squeeze the two geomembranes  intimately together,  see
           Figure 7.6 for details.
                                     73

-------
 Figure  7.5(a).  Two sheets of  liner being cleaned  and
                prepared for trial seaming.
Figure 7.5(b).   The two sheets being seamed together thereby
                forming the test strip.
                         74

-------
Figure 7.5(c).  The completed test strip being cut into individual  samples
                for subsequent inspection and destructive testing.
     Figure 7.5(d).  Marking the test strip samples for identification
                    and records.

                                    75

-------
                                                                   Joined
                                                                   Geomembranej
                                      Hot Wedge
                           Direction of Travel
Figure 7.6.  Details of the hot wedge  system showing relative positions
             of the hot wedge, rollers and  sheets to be joined.

                                   76

-------
(c)   The type of geomembrane, rate of seaming, and ambient factors
      such as clouds, wind, and hot sun require the temperature setting
      of the wedge to vary.   Depending upon the records to be kept,
      one might record a number of different temperatures.  For
      example, the temperature of the hot wedge, the temperature of the
      sheet after seaming, the temperature of the sheet away from the
      seaming area and the ambient temperature.  This is a site
      specific decision usually determined by the contract
      specification or CQC/CQA Documents.

(d)   Power for the drive motor should be off when positioning the
      machine to make a seam.  Manually place the machine within the
      overlapped sheet of material.  The sheets shall be guided between
      the idlers and the wedge, and into the drive/nip rollers.  This
      procedure is only possible when starting with two new sheets.
      When starting a weld in the middle of two sheets, the material
      must be loaded from the sides.  The machine is to be picked up a
      few inches,  loading the bottom sheet first, and then the top
      sheet.  As soon as the nip rollers are engaged and the wedge is
      in position, the power to the drive motor should be turned on.
      Once the sheets are between the nip rollers, they shall  be
      engaged immediately, otherwise a melt-through will occur within a
      few seconds.  The hot wedge should be moved into position and
      locked.

(e)   It is necessary that the operator keep constant visual contact
      with the temperature controls, as well as the completed seam
      coming out of the machine.  Occasional adjustments of temperature
      or speed as  the result of changing ambient conditions will  be
      necessary to maintain a consistent seam.   Constant visual and
      hands on inspection is also recommended.   If changes in the
      welding conditions are made as a response to a changing welding
      environment, the testing of an additional destructive sample
      shortly after the change is recommended.

(f)   On some soils,  the device may "bulldoze"  into the ground as it
      travels.  This causes soil to enter the seam area, making the
      seam weak and unacceptable.  To overcome  this, it is recommended
      that the operator take some of the weight off of the front of the
      machine by lifting it slightly.   Alternatively, some type of base
      for the machine to travel on should be provided.   Strips of
      geotextile or geomembrane have proven effective to prevent this
      bulldozing effect.  Depending on the soil conditions it may be
      necessary to change the size of the rollers in loose soils.   It
      is necessary that at least two people work together in making hot
      wedge seams; one operator and one helper.

(g)   A fully leak-proof T-connection is necessary wherever
      intersecting seams are to be joined together.   At such locations,
      the hot wedge device must be removed a short distance
      (approximately 15 cm or 6 inches) from the intersecting seam.
                                77

-------
           For HOPE and VLDPE this short distance  must  be  completed  by
           extrusion fillet seaming,  see Figure  7.7.  Note that  the  unbonded
           free overlaps of the  sheets  are  to  be cut  away  to  expose  the edge
           of the outside of the hot  wedge  seam.  The surface must be  ground
           to remove the surface oxide,  see Section 5.   The extrudate  bead
           is then placed in a continuous fashion  so  as to provide complete
           coverage of all  areas not  completed by  the hot  wedge  device.

     (h)    For a leak proof T-connection in PVC, CSPE,  CPE and EIA
           materials, the short  distance referred  to  in (g) above must be
           completed by chemical bonding (fusion)  or  chemical  adhesive.


7.5  AFTER SEAMING

     (a)    A smooth insulating plate  or heat insulating fabric is to be
           placed beneath the hot welding apparatus after  usage.

     (b)    For HOPE and VLDPE a  slight  amount  of "squeeze-out" or  "flashing"
           is a good indicator that the proper temperatures were achieved,
           see the sketch of Figure 7.8. It signifies  a proper  seam in that
           some of the melted polymer was laterally squeezed  out of  the seam
           zone.  If an excessive amount of hot  melt  is being squeezed out,
           it is an indication of either too much  heat, too much pressure,
           or too slow a seaming rate.   Reduce the temperature and/or
           pressure and/or adjust the rate  to  correct the  situation.

     (c)    For VLDPE liners of 1.0 mm (40 mils)  thickness  a long,  low
           wavelength pattern in the  direction of  the seam along its top
           surface is indicative of a proper weld. If  the wave  peaks  become
           too close together, the machine  speed should be increased until a
           satisfactory pattern  is present.  The absence of this wavelength
           pattern indicates that the machine  speed should be decreased.
           There will be no wavy pattern for VLDPE liners  greater  than 1.0
           mm (40 mils) in thickness  due to the  inherent stiffness of  the
           thicker material.

     (d)    Nip/drive roller marks may show  on  the  surface  when using knurled
           rollers.  Their depth should be  visually observable,  but  care
           should be taken to insure  that the nip  drive rollers  do not
           create a rut, e.g. the indentation  should  be barely capable of
           being felt.

     (e)    The hot wedge device  has only a  few adjustments that  can  be made,
           but it is very important that they be checked regularly.
           Cleaning of the machine should be done  at  least daily.

     (f)    The seam must be checked visually for uniformity of width and
           surface continuity.  Usually the installer will use a vacuum box
           or "air lance" depending on  the  geomembrane  material  to  check for
           voids or gaps in the  seam.  For  dual  wedge seams the  air  channel
           can be used to evaluate seam integrity.

                                     78

-------
                                 Extrudate
                                -^'f
                           Extrudate
                                                            Hot Shoe
                                                           Fusion Weld
SECTION
     r
                                       fillet extrusion bead
           Figure 7.7.  Hot  wedge T-seam  detail.

                              79

-------
Upper Geomembrane
  ^Squeeze-Out" or
     "Flashing"
                typ. 12 mm
                 (0.5 in.)
typ. 12 mm
 (0.5 in.)
typ. 12 mm
 (0.5 in.)
                                                                Lower Geomembranf
                      Cross  Section of Dual  (Split)
                             Hot Wedge Seam


       Figure 7.8.  Schematic diagram of cross section of dual (split)
                    hot wedge seam illustrating squeeze-out.
     (g)   When unbonded areas are located they should be patched with at
           least 15 cm (6 inches) of geomembrane extending on all sides.
           Any area of the geomembrane where puncture holes are observed
           they must be patched as above with at least 15 cm (6 inches) of
           geomembrane extending beyond the affected areas.  If grinding is
           to be performed to prepare the geomembrane, review instructions
           provided in Section 5.

     (h)   Photographs of cross sections of different types of hot wedge
           seams follow in Figure 7.9.
7.6  UNUSUAL CONDITIONS

     This section is written to give insight into conditions which go beyond
the general  description just presented.

     (a)   High winds, or gusts of wind, are always problematic for liners.
           After placing the geomembrane, the panels or rolls must be
           adequately ballasted, e.g., with sandbags.  The actual seam
           fabrication, however, may require the removal of some of the
           sandbags leaving the windward edge vulnerable to wind uplift
           forces.  If possible, proper orientation of the overlap might be
           helpful. Otherwise,  additional labor may be required to remove
           sandbags immediately in front of the seaming operation.  The
           liner must be cleaned of any dirt and moisture left behind after
           sandbag removal.  They are then to be replaced behind the
           completed seaming operation.
                                     80

-------
Figure 7.9.   Photographs of cross sections of HOPE hot wedge seams.
             Upper:    Single hot wedge seam with acceptable
                      squeeze-out
             Middle:   Dual  hot wedge seam with excessive squeeze-out
             Lower:    Dual  hot wedge seam with acceptable squeeze-out

                                81

-------
(b)    Patches are necessary at  locations  where  destructive  test samples
      are removed or where seams are shown  to fail  nondestructive
      testing.  These patches must extend a minimum of 15 cm (6 inches)
      beyond the outer limits of the area to be repaired.  For HOPE
      liners the only method available is a hand held extrusion fillet
      procedure as described in Section 5.   Particular care must be
      exercised when the end of the extrudate meets the beginning of
      the run.  The double heat that the  polymer will necessarily
      experience cannot be excessive,  i.e., a large mass of extrudate
      should not be visible at  this location.   For other geomembrane
      types, one or more of the following methods may be used; hot air,
      chemical or adhesive. These will be  described in subsequent
      sections.

(c)    Details around sumps, pipes and other appurtenances are perhaps
      the most demanding seams  in a facility.   Also due to  their
      typical locations being at low points of  the containment
      facility's design, these  areas inherently operate under larger
      hydraulic heads.  Should  a defect from improper seaming occur in
      such a location leakage rates and its associated adverse impacts
      are heightened.  Therefore, extreme care  should be exercised in
      ensuring seam integrity  in these often difficult to reach
      locations.  For HOPE and  VLDPE the  extrudate should be symmetric
      on both liners to be joined which is  difficult for external and
      internal edges and particularly at  corners.  The end  of the seam
      run, where it joins to the beginning, should be a smooth
      transition and not end with a large mass  of extrudate.  For HOPE
      and VLDPE liners these details must necessarily be made by hand-
      held extrusion fillet procedures as described in Section 5.  For
      PVC, CSPE, EIA and CPE type geomembranes, either hot  air,
      chemical or adhesive methods may be used.

(d)    This section was written  for material temperatures that range
      between O'C (32F) and 50C (122'F).   This is the temperature
      range that is generally  recognized as being acceptable for
      seaming without taking special precautions.

      For sheet temperatures below 0"C (32*F),  shielding, preheating,
      and/or a slower seaming  rate may be required.  More frequent seam
      testing and precautions  to prevent thawing subgrade (previously
      discussed) may have to be taken.  Sharp,  frozen subgrade should
      be avoided to eliminate  point pressure damage potential.

      For sheet temperatures above 50C (122'F), shielding  and rate of
      seaming should be adjusted.  More frequent destructive seam
      testing may have to be taken.
                                82

-------
FIELD NOTES:
                                     83

-------
FIELD NOTES:
                                      84

-------
                                   SECTION 8

                            DETAILS OF  HOT AIR  SEAMS
     Hot air seams represent an applicable seaming method for all geomembranes
listed in Table 4.2.
8.1  GEOMEMBRANE PREPARATION

     (a)   Note, that this document assumes that the proper geomembrane has
           been visually inspected to ensure it is free of deep scratches, or
           defects that would cause the sheet to not meet specifications of the
           installation.  It is further assumed the sheet has been delivered to
           the site and brought to its approximate plan position for final
           installation and seaming.   Only the material that can be seamed that
           day should be deployed.  All deployed material should be ballasted
           as required to prevent wind uplift.

     (b)   If the geomembrane is CPE, CPE-R, CSPE-R, EIA, EIA-R, PVC,  or
           PVC-R and in some cases VLPDE,  it will  usually arrive on site in the
           form of fabricated panels  which are accordion-folded in both
           directions.  They are generally packaged in palletized, heavy
           cardboard containers.  If  the geomembrane is VLDPE (generally) or
           HOPE, it will arrive on the site in rolls.

     (c)   The geomembrane should remain packaged  or rolled and dry until ready
           for use.  The material should not be unfolded or unrolled if the
           material temperatures are  lower than -10C  (14F) due to the
           possibility of cracking.  If the liner  is stored in a warm place,
           e.g. 10"C (50F) or above, prior to being unfolded or unrolled on
           site, then it can be placed at  -18C (O'F)  or below temperatures
           providing the time between removing the geomembrane from storage and
           deployment does not exceed one-half working day.  Geomembrane
           deployment may be allowed  under other conditions but the CQC/CQA
           Documents and/or project specifications must be specific as to the
           conditions.

     (d)   The two geomembrane sheets to be joined must be properly positioned
           such that approximately 7.5 cm  to 15.0  cm (3 to 6 inches) of overlap
           exists.  All  personnel walking  on the geomembrane should have smooth
           soled shoes.   Heavy equipment,  e.g.  pickups, tractors,  etc. should
           not be allowed on the geomembrane at any time, unless otherwise
           specified by the manufacturer and approved  in the CQC/CQA Documents.
                                      85

-------
(e)    If the overlap is insufficient and it  does  not  fully cover the air
      flow nozzle,  lift the sheet up to  allow air beneath  it  and "float"
      it into proper position.   Avoid dragging geomembrane sheets made
      from HOPE particularly when they are on rough soil subgrades since
      scratches in  the material  may create various stress  points of
      different depths and  orientations.

(f)    When most reinforced  geomembranes  are  cut to accommodate  odd shapes
      or to fit small  pieces,  resealing  of the exposed  scrim  by flood
      coating is required by the use of  manufacturer's  or  fabricator's
      approved liquid sealant.

(g)    If the overlap is excessive when placing HOPE and VLDPE and is to be
      removed, it should be done by trimming the  lower  sheet.   If this is
      not possible  and the  upper sheet must  be trimmed,  do not  use a knife
      with an unshielded blade  to cut off the excessive amount  because the
      blade facing  downward can easily scratch or cut into the  underlying
      geomembrane in a very vulnerable location.   A shielded  blade or a
      hook blade should be  used to trim  off  the excess  geomembrane.   A
      photograph of such a  device is shown in Figure  8.1.   Whenever
      possible it should be used from beneath the liner in an upward
      cutting motion.   For  liners made from  CPE,  CPE-R,  CSPE-R, EIA, EIA-
      R, PVC or PVC-R and VLDPE the excess material can be cut  by
      scissors, see Figure  8.2  or can be worked away  from  the edges of the
      seam to maintain proper overlap.

(h)    All cutting and preparation of odd shaped sections or small fitted
      pieces should be accomplished at least 15 m (50 ft.) ahead of the
      seaming operation so  that seaming  can  be completed with as few
      interruptions as possible.

(i)    The two opposing geomembrane sheets to be joined  should visually be
      checked for defects of sufficient  magnitude to  affect seam quality.
      The criteria  to be met and the procedures to be used in this regard
      should be stipulated  in the contract specifications  and/or in the
      CQC/CQA Documents.

(j)    If the construction plans require  overlaps  to be  shingled in a
      particular direction  this should be adhered to  and verified.

(k)    Excessive undulations (waves) along the seams during the  seaming
      operation should be avoided.  When this occurs  due to either the
      upper or lower sheet  having more slack than the other or  because of
      thermal expansion and contraction,  it  often leads to the  undesirable
      formation of "fishmouths" which must be trimmed,  laid flat and
      reseamed with a patch.  An example of  a fishmouth and its correction
      is shown in Figure 8.3(a-d).
                                 86

-------
 Figure  8.1.
Trimming of excess geomembrane to obtain proper overlap
prior to seaming.
Figure 8.2.   Type of scissors recommended for cutting of geomembranes.
                                  87

-------
Figure 8.3(a).   Formation of "fishmouth"  with  excessive  slack  in
                upper geomembrane  versus  lower geomembrane.
        Figure 8.3(b).   Cutting  of  "fishmouth"  along  its centerline.
                                 88

-------
     Figure 8.3(c).  Overlapping and seaming the ends  of the upper
                     geomembrane to the lower geomembrane.
Figure 8.3(d).   Patch over the entire  area where  "fishmouth"  was  located.

                                   89

-------
(1)   There generally should be some slack in the installed liner which
      depends on the type of geomembrane, the ambient and anticipated
      service temperatures, length of time the geomembrane will be
      exposed, location of the facility, etc.  This is a design
      consideration and the Plans and Specifications must be project
      specific on the amount and orientation of this slack.

(m)   The sheets which are overlapped for seaming must be clean.   If
      dirty, they must be cleaned with dry rags and other appropriate
      materials.

(n)   The sheets which are overlapped for seaming must be free of moisture
      in the seam area.

(o)   Seaming is not allowed during rain or snow, unless proper
      precautions are made to allow the seam to be made with dry
      geomembrane sheets, e.g.,  within an enclosure or shelter.

(p)   It is preferable not to have water-saturated soil beneath the
      geomembrane during installation.  Seaming boards help in this regard
      by lifting the seams off the soil subgrade.

(q)   If the soil beneath the geomembrane is frozen,  the heat from hot air
      seaming devices or any preheating lamps that may be used can thaw
      the frost allowing water to be condensed onto the unbonded  region
      ahead of the seam being fabricated.  This possibility may be
      eliminated by the use of suitable seaming boards or slip sheets made
      from excess geomembrane material.

(r)   Ambient temperatures for seaming should be above freezing,  i.e. 0C
      (32'F), unless it can be proven with test strips that good  seams can
      be fabricated at lower temperatures.  However,  temperature  is less
      of a concern to good seam quality than is moisture.

(s)   For cold weather seaming,  it may be advisable to preheat the sheets
      with a radiant heater or hot air blower, to use a tent of some sort
      to prevent heat losses during seaming and to make numerous  test
      seams in order to determine appropriate seaming conditions,  e.g.,
      equipment temperatures may have to be set higher and/or seaming
      rates slowed down during cold weather seaming.

(t)   Sheet temperatures for seaming should be below 50C(122F)  as
      measured by an infrared thermometer or surface contact thermocouple.
      It is recognized that depending on material, type and thickness,
      higher temperatures may be allowed.  It should also be recognized
      that wind and cloud cover  will  determine the actual sheet
      temperature.  High temperatures affect not only worker performance
      but will also affect durability of some geomembranes unless  special
      precautions, e.g. tents,  etc.,  are taken.  For temperatures  above
      this value special attention should be paid to the seaming,  frequent
      test strips and more diligent nondestructive testing is recommended.
      NOTE:  For items (q),  (r), (s,) and (t) the CQC/CQA Documents and/or

                                 90

-------
           project specifications and the regulatory requirements regarding hot
           and cold temperature seaming limitations should be reviewed to avoid
           possible problems with final construction certification acceptance.


8.2  EQUIPMENT PREPARATION

     (a)   Properly functioning portable electric generators must be available
           within close proximity of the seaming region and with adequate
           extension cords to complete the entire seam.  These generators
           should be of sufficient size or numbers to handle all seaming
           electrical requirements.   The generator must have rubber tires,  or
           be placed on a smooth plate such that it is completely stable so
           that it cannot damage the geomembrane or to the underlying clay
           liner or subgrade material.  Fuel  (gasoline or diesel) for the
           generator must be stored  off the geomembrane and if accidently
           spilled on the geomembrane it must be immediately removed.  The  area
           should be inspected for damage to the geomembrane and repaired if
           necessary.

     (b)   Hot air seaming devices are of two different types:  the manual,
           hand-held type and the automatic,  machine-driven type.  Photographs
           of each type are shown in Figure 8.4.

     (c)   If a gas, other than air, is to be used,  an ample supply should  be
           available.

     (d)   A manual, hand-held instrument should be checked to  see that the air
           intakes are not obstructed and that the nozzle is of the proper  type
           and width and that it is  free from obstructions which could limit a
           uniform flow of air.  Care should  be taken in choosing the nozzle
           design and magnitude of the pressure.  If excessive  air is
           discharged under the top  geomembrane it could create a backpressure
           that may blow dust or small soil  particles into the  seam area.   The
           temperature should be capable of being monitored either with an
           instrument gage or adjustment on the device or with  a separate
           temperature indicator.  Typical  temperature ranges for seaming
           various geomembranes are  given in  Table 8.1.

     (e)   For the automatic, machine-driven  type of hot air seaming equipment
           there are a number of important  details.   As  before,  the air-flow
           nozzle and temperature  should be inspected to see that a constant
           flow of air at the proper temperature is  being supplied.   Figure 8.5
           gives general  details of  the system showing the relative positions
           of the various parts.

     (f)   The air-flow nozzle should be checked to  see  if a single track or a
           dual  track seam is to be  fabricated.   If  the  latter,  the nozzle  will
           be subdivided at its exit end into  separated  air flow channels.
                                      91

-------
Figure 8.4.  Various types of hot air seaming devices.
             Upper photograph is a manual  hand-held type;
             Lower photograph is an automatic machine-driven type.

                             92

-------
     TABLE 8.1.  TYPICAL TEMPERATURE RANGES FOR HOT AIR SEAMING OF
                 GEOMEMBRANES (I.E., AS THE AIR EXITS THE CHAMBER).
Geomembrane
Type
CPE
CPE-R
CSPE-R
EIA
EIA-R
HOPE"*
PVC
PVC-R
VLDPE*"
Minimum*
C CF)
245 (475)
245 (475)
245 (475)
370 (700)
370 (700)
400 (750)
370 (700)
370 (700)
350 (660)
Maximum**
*C CF)
650 (1200)
650 (1200)
650 (1200)
650 (1200)
650 (1200)
650 (1200)
650 (1200)
650 (1200)
650 (1200)
*    For dry, warm weather seaming conditions

**   For damp, cold weather seaming conditions

***  For textured or roughened HOPE or VLDPE sheet increase temperatures
     about 40C (72"F).  Also, slower seaming rates and higher pressures
     may be required.
                                   93

-------
               Lower FML
                                             Nozzle
                                                                     Seamed FML
                                       Direction of Travel
             Figure 8.5.   Cross  section of  automated machine-driven  hot  air
                          seaming device  for geomembranes.
I
(g)   Knurled rollers are used for applying pressure on the sheets and
      driving the device.  They immediately follow the air nozzle.  The
      knurled rollers should be inspected to ensure there are no sharp
      surfaces and that wheels are smoothly beveled on the edges.

(h)   If a chain drive powers the device and applies pressure to the
      nip/drive rollers it should be inspected for synchronization of
      travel, proper functioning and fit.  Loose chains or damaged
      sprockets should be repaired or replaced.

(i)   As the geomembrane sheet materials pass through the machine, they
      should come in contact with air from the full width of the air
      nozzle in order to heat the material properly and uniformly.  On
      some devices idler rollers on both sides of the device are
      adjustable and must make the material conform as it passes through
      the machine.

(j)   The front part of the seaming device should be inspected for sharp
      corners and irregular details which may damage the geomembrane or
      cause sheet hang-up.
                                             94

-------
     (k)   If available, temperature controllers on the device should be set
           according to type of geomembrane, the thickness, the ambient
           temperature, and the rate of seaming.  Table 8.1 gives typical
           values but this is a site and material specific decision usually
           determined by the contract specification or CQC/CQA Documentation.

     (1)   If available, the force sensors at the nip rollers should be
           checked for accuracy and repeatability.


8.3  TEST STRIPS

     A general requirement of most CQA Documents is that "test seams" or
"test strips" be made on a periodic basis.  Test strips generally reflect the
quality of field seams but should never be used solely for final field seam
acceptance.  Final field seam acceptance should be specified in the contract
specification and should include a minimum level of destructive testing of
the production field seams.  Test strips are made to minimize the amount of
destructive sampling/testing which requires subsequent repair of the final
field seam.  Typically these test seams, for each seaming crew, are made
about every four hours, or every time equipment is changed, or if significant
changes in geomembrane temperature are observed, or as required in the
contract specification.  This is a recommended practice that should be
followed when seaming all types of geomembranes.  The purpose of these tests
is to establish that proper seaming materials, temperatures, pressures,
rates,  and techniques along with the necessary geomembrane pre-seaming
preparation is being accomplished.  Test strips may be used for CQA/CQC
evaluation, archiving, for exposure tests, etc., and must be of sufficient
length to satisfy these various needs.

     Each seaming crew and the materials they are using must be traceable and
identifiable to their test seams.   While the test seams are being prepared,
cured,  and CQC tested, the seaming crew may continue to work as long as the
seams they have made (and are making) since their last acceptable test sample
strip was prepared, are completely traceable and identifiable.   If a test
seam fails to meet the field seam design specification, then an additional
test seam sample will have to be made by the same seaming crew - using the
same tools, equipment and seaming materials - and retested.

     The liner's finished field seams will not be accepted unless the before
and after "test seam sample strip" CQC test results (or other CQC seam test
result criteria as required per the design specification) are acceptable per
the site's design specifications.   If a seam is not accepted, destructive
testing of samples from the actual seam will be removed from the liner and
tested.  If the actual seam destructive test results still  do not meet the
design specification requirement,  then the unacceptable seams will  all have
to be repaired or reconstructed with seaming materials by a test proven
seaming crew that has passed its testing requirements.  The procedure
illustrated in the flow chart of Figure 8.6 must be followed.  Note that the
failure of test strip 1 requires two actions:  (a) the making of test strip
2, and  (b) an increased frequency of destructive tests on production field
seams made during the curing of test strip 1 (if any were made).   This

                                     95

-------
I
                                                     'Mot*: S*tm/ng CnwFilling to Pnptn
                                                       AccipttUt TtaStrtptUiyfttguIn
                                                       attaining InAeeonltnet with COC/COA Ooamtntt
                               Figure 8.6.   Test strip  process flow  chart.
                                                        96

-------
increased frequency must be stipulated in the contract specifications or in
the CQC/CQA Documents.

     If the destructive seams fail or if test strip 2 fails, production field
seaming is halted.  All production field seams made during the interval are
repaired per the contract specifications or CQC/CQA Documents to the point of
previous acceptance with an approved seaming crew.

     At this point, the seaming crew that failed to pass both strip tests
must adjust and recertify current seaming equipment and technique or obtain
new seaming equipment, tools and/or retrain personnel and begin making
initial test strip samples.

     For hot air seams, test strips of the type shown in Figure 8.7(a-d) are
prepared.  The seam is centered lengthwise between the two sheets to be
joined.  Figure 8.7(a) shows the geomembrane to be seamed being cut and
prepared for seaming, 8.7(b) shows the actual test strip being seamed, 8.7(c)
shows the sampling of the test strip for subsequent destructive testing, and
8.7(d) shows the individual samples cut from the test strip being identified.
For geomembranes that are seamed by thermal methods, the seams can be tested
after they are allowed to cool in ambient air at least 5-10 minutes or longer
prior to shear and peel testing.

     As previously stated, all seam test samples must be prepared in
triplicate sets preferable in a continuous seam which can be cut in thirds;
one set for CQC tests, one set for CQA tests and one set made available to
(or retained for) the agency/owner/design organization.   If referee test
results are required, CQA test results from destructive testing of actual
seam samples will prevail.

     During the CQC and CQA test requirement periods, a liner should not be
covered and it cannot be placed into service.  This will insure the ease and
viability of repairing or reconstructing in the event it is required.   During
this period it is imperative that the liner be properly ballasted and
otherwise secured so as to prevent wind or unusual weather damage.


8.4  ACTUAL SEAMING PROCESS FOR THE MANUAL, HAND-HELD TYPE OF HOT AIR SEAMING

     (a)   The hot air system should be properly positioned for the making of
           the desired seam, see Figure 8.8.  Note the position of the
           hand-held roller immediately behind the gun.

     (b)   The principle of the technique is that the hot air is to melt the
           surface of both the lower and the upper geomembrane followed
           immediately by roller pressure to intimately join the melted
           viscous surfaces of the materials.  Uniformity of melting across
           the entire surface to be joined is an important detail.  Excessive
                                     97

-------
Figure 8.7(a).  Geomembrane being cut and prepared for trial seaming.
      Figure 8.7(b).  The two sheets being seamed together thereby
                      forming the test strip.

                                 98

-------
Figure 8.7(c).  The completed test strip being cut into individual  samples
                for subsequent inspection and destructive testing.
   Figure 8.7(d).   Marking the test strip samples  for identification
                   and records.

                                   99

-------
                                 4
  Figure 8.8.   Fabrication of a field seam using manual  hand-held
               hot air seaming technique.
      melting as well  as inadequate melting must be avoided.   Note that
      the roller pressure is exerted manually.

(c)    Temperature and  dwell  time will  vary according to the geomembrane
      type,  thickness  and the ambient temperature.   These variables, in
      turn,  will dictate the rate of seaming.

(d)    Other  ambient factors  such as sun,  clouds, wind and humidity will
      require alterations to the seaming  rate.   This is a site specific
      consideration.

(e)    It is  necessary  that the seamer(s)  keep  constant visual  contact
      with the completed seam.

(f)    It is  sometimes  advantageous to have two man  work crews; one with
      the hot air gun,  the other with the roller.  The second  person is
      then somewhat free to  do visual  and hands on  inspection.

(g)    Excessive surface deformation indicating too  much heat,  or too
      slow of a travel  rate, are obviously not permitted.
                                100

-------
8.5  ACTUAL SEAMING PROCESS FOR THE AUTOMATED, MACHINE-DRIVEN TYPE OF HOT AIR
     SEAMING

     (a)   The hot air equipment should be properly positioned for the making
           of the desired single or dual (split) seam, see Figure 8.9(a-b).

     (b)   As mentioned previously, the principle of the hot air seaming
           technique is that both surfaces to be joined come into intimate
           contact with one another after reaching the proper temperature.
           Contact is automatically controlled via the rollers which create
           pressure such that intermingling of the material from both sheets
           occurs.

     (c)   Typical temperature settings will vary according to the type and
           thickness of geomembrane being installed, the ambient temperature
           and the rate of travel.  The CQC/CQA Documentation should be
           reviewed for appropriate temperature ranges.

     (d)   Ambient factors such as sun, clouds, wind, and humidity will
           require the seaming rate to vary.  This is a site specific
           condition.

     (e)   Power for the drive motor should be off when positioning the
           machine to make a seam.  Manually place the machine within the
           overlapped sheets of material.  The sheets shall be guided beneath
           and above the air nozzle, and into the drive/nip rollers.  This
           procedure is only possible when starting with two new sheets.
           When restarting a partially completed run in the middle of two
           sheets, the material must be loaded from the sides.  The machine
           is to be picked up a few inches, loading the bottom sheet first,
           and then the top sheet.  As soon as the nip rollers are engaged,
           the hot air should be supplied to the sheets and the power to the
           drive motor should be turned on.

     (f)   It is necessary that the operator keep constant visual contact
           with the completed seam coming out of the machine.  Occasional
           adjustments of temperature or speed will be necessary to maintain
           a consistent seam weld.

     (g)   On some soils, the machine may "bulldoze" into the ground as it
           travels.  This causes soil to enter the area to be seamed, making
           the seam weak and unacceptable.  To overcome this, it is
           recommended that the operator take some of the weight off the back
           of the machine by lifting it slightly.  Alternatively, some type
           of base for the machine to travel on could be provided.  Strips of
           geotextile or geomembrane have proven effective to prevent this
           bulldozing effect.  It might be required to change the size of the
           rollers.  It is recommended that at least two people work together
           in making hot air seams; one operator and one helper.
                                     101

-------
             Figure 8.9(a).  Fabrication of a field seam using automated, machine
                             driven hot air seaming technique (side view).
I
             Figure 8.9(b).  Fabrication of a field seam using automated, machine
                             driven hot air seaming technique (top view).

                                             102

-------
     (h)   A leak-proof T-connection is necessary wherever intersecting seams
           are to be joined together.  At such locations when HOPE or VLDPE
           geomembrane is used, the hot air device must be removed a short
           distance (approximately 15 cm or 6 inches) from the intersecting
           seam.  This short distance must be completed by hand held hot air
           seaming, or by extrusion fillet seaming, see Figure 8.10.  Note
           that the unbonded free overlaps of the sheets are to be cut away
           to expose the edge of the outside of the hot air seam.  The
           extrudate bead is then placed in a continuous fashion so as to
           provide complete coverage of all areas not completed by the hot
           air device.

     (i)   For leak proof T-connections in PVC, CSPE, CPE and EIA materials,
           the short distance referred to in (h) above must be completed by
           chemical bonding (fusion) or chemical adhesive.


8.6  AFTER SEAMING

     (a)   A smooth insulating plate or heat insulating fabric is to be
           placed beneath the hot seaming apparatus after usage to avoid
           damage to the geomembrane.

     (b)   A slight amount of "squeeze-out" or "flashing" is a good indicator
           that the proper temperatures were achieved, see the sketches of
           Figure 8.11.  It signifies a proper seam in that some of the
           melted polymer was laterally squeezed out of the seam zone.  If an
           excessive amount of hot melt is being squeezed out, it is an
           indication of either too much heat,  too much pressure, or too slow
           a seaming rate.  Reduce the temperature and/or pressure and/or
           adjust the rate to correct the situation.

     (c)   For VLDPE liners of 1.0 mm (40 mils) thickness, a long, low
           wavelength pattern in the direction  of the seam along its top
           surface is indicative of a proper weld.  If the wave peaks become
           too close together, the machine speed should be increased until  a
           satisfactory pattern is present.  The absence of this wavelength
           pattern indicates that the speed should be decreased.  There will
           be no wavy pattern for VLDPE liners  greater than 1.0 mm (40 mils)
           in thickness due to the inherent stiffness of the thicker
           material.

     (d)   Nip/drive roller marks may show on the surface when using knurled
           rollers.  Their depth should be visually observable,  but care
           should be taken to insure that the nip drive rollers do not create
           a rut, e.g. the indentation should be barely capable of being
           felt.

     (e)   The hot air seaming device has only  a few adjustments that can be
           made, but it is very important that  they be checked regularly.
           Cleaning of machine should be done at least daily.


                                     103

-------
                                       Extrudate
                                  Extrudate
                                                                /Hot  air fusion
                                                                weld
       SECTION
                                             fillet extrusion bead
Figure 8.10.   Dual  track hot  air  machine T-seam detail  for HOPE or  VLDPE.

                                     104

-------
         Upper Geomembrane
   "Squeeze-Out" or
      "Flashing*
                                typ. 25-75 mm
                                   (1-3 in.)
                           Lower Geomembrane
         Upper Geomembrane
    "Squeeze-Out" or
       "Flashir
                     typ. 12 mm
                      (0.5 in.)
typ.  12 mm
 (0.5 in.)
typ.  12 mm
 (0.5 in.)
                                                          Lower Geomembrane
      Figure 8.11.   Schematic diagrams of cross sections  of single and
                     dual  (spilt) hot  air seams illustrating squeeze-out.


     (f)   The seam must be checked visually  for uniformity  of width and
           surface continuity.  Usually the installer will use a vacuum box
           or air lance to check for voids or gaps  in the  seam.

     (g)   When unbonded areas are located, they should  be patched  with at
           least 15 cm (6  inches) of geomembrane extending on all sides.  Any
           area of the geomembrane where puncture holes  are  observed must  be
           patched as above with at least 15  cm (6  inches) of geomembrane
           extending beyond the affected areas.

     (h)   Photographs of  cross sections of hot air seams  follow in
           Figure 8.12.


8.7  UNUSUAL CONDITIONS

     This section is written to give insight  into conditions which  go beyond
the general description just presented.

     (a)   High winds, or gusts of wind, are  always  problematic for liners.
           After placing the geomembrane, the panels or  rolls must  be
           adequately ballasted, e.g., with sandbags.  The actual seam
           fabrication, however, may require  the removal of  some of the
           sandbags leaving the windward edge vulnerable to  wind uplift
           forces.
                                     105

-------
Figure 8.12.   Cross sections of EIA-R liner (single  track)  seams  fabricated
              by the hot air method showing left,  center,  and  right  sides  of
              completed seam (light colored lines  are  the  reinforcing  fabric
              yarns).

                                     106

-------
      If possible, proper orientation of the overlap might be helpful.
      Otherwise,  additional  labor may be required to remove sandbags
      immediately in front of the seaming operation.  The liner must be
      cleaned of any dirt and moisture left behind after sandbag
      removal.  They are then to be replaced behind the completed
      seaming operation.

(b)   Patches are necessary at locations where destructive test samples
      are removed or where seams are shown to fail nondestructive
      testing.  These patches must extend a minimum of 15 cm (6 inches)
      beyond the outer limits of the area to be repaired.  For HOPE and
      VLDPE liners,  another method available is the hand-held extrusion
      fillet procedure described in Section 5.   Particular care must be
      exercised when the end of the run meets the beginning of the run.
      The double heat that the polymer will necessarily experience
      cannot be excessive.  For other geomembrane types, one or more of
      the following  methods may be used; hot air,  chemical or adhesive
      methods be used.  These will  be described in subsequent sections.

(c)   Details around sumps,  pipes and other appurtenances are perhaps
      the most demanding locations to properly seam in an entire
      facility.  Also due to their typical  locations being at low points
      of the containment facility's design, these areas inherently
      operate under  larger hydraulic heads.  Should a defect from
      improper seaming occur in such a location leakage rates and its
      associated adverse impacts are heightened.   Therefore, extreme
      care should be exercised in ensuring seam integrity in these often
      difficult to reach locations.  For HOPE and VLDPE liners these
      details must necessarily be made by hand held hot air or extrusion
      fillet procedures. For PVC, CSPE, CPE and EIA either hot air or
      chemical fusion procedures can be used.

(d)   This section was written for material temperatures that range
      between 0C (32'F) and 50C (122*F).   This  is the temperature
      range that is  general  recognized as being acceptable for seaming
      without taking special  precautions.

      For sheets  below 0C (32F),  shielding,  pre-heating, and/or a
      slower seaming rate may be required.   More  frequent seam testing
      and precautions to prevent thawing subgrade (previously discussed)
      may have to be taken.   Sharp, frozen subgrade should be avoided to
      eliminate point pressure damage potential.

      For sheet temperatures  above 50*C (122F),  shielding and rate of
      seaming should be adjusted.  More frequent  destructive seam
      testing may have to be  taken.
                                107

-------
FIELD NOTES:
                                     108

-------
                                   SECTION 9

             DETAILS OF CHEMICAL AND BODIED CHEMICALLY-FUSED SEAMS


     As is shown in Table 4.2, chemically-fused seams are an applicable field
seaming method for PVC, CPE, CSPE, and EIA liners, both reinforced and
unreinforced.  Fusion chemicals may be either bodied (thickened) or nonbodied.
The application and seaming procedure for the use of either one is basically
the same.  Bodied fusion chemicals are thickened with materials that are also
common to the geomembrane itself.  They may be used interchangeably with non-
bodied fusion chemicals; however, they are more commonly used to increase the
dwell or working time, seal exposed fabric or scrim edges or on slopes to
prevent rapid run-off of the seaming chemical.  This section focuses on the use
of both forms of fusion chemicals as through they were a single entity for
field seaming compounded thermoplastic and thermoplastic elastomeric
geotnembranes.


9.1  GEOMEMBRANE PREPARATION

     (a)   Note that this document assumes that the geomembrane has been
           visually inspected to ensure it is free of deep scratches or defects
           that would cause the sheet to not meet the specifications of the
           installation.   It is further assumed the sheet has been delivered
           to the site and brought to its approximate plan position (as per the
           design panel layout) for final installation and seaming.  Only the
           material that can be seamed that day should be deployed.  All
           deployed material should be ballasted as required to prevent wind
           uplift.

     (b)   The geomembrane will usually arrive on site in the form of
           prefabricated panels which are accordion folded in both directions.
           These panels are usually packaged in palletized,  heavy weatherable
           cardboard containers.

     (c)   The geomembrane should remain packaged and dry until ready for use.
           The material should not be unfolded when material temperatures are
           lower than -10'C (14F) due to the possibility of cracking.   If the
           panel  is stored in a warm place,  e.g. 10C (50F) or above,  prior to
           being unfolded on site, then it can be placed at  -18C (0F) or
           below temperatures, providing the time between removing the
           geomembrane from storage and deployment does not  exceed one-half
           working  day.  Geomembrane deployment may be allowed for other
           conditions but the CQC/CQA Documents and/or project specifications
           must be  specific as to the conditions.


                                      109

-------
(d)    All  personnel  walking  on the geomembrane  liner should  have smooth-
      soled shoes.   Heavy equipment,  e.g.  pickups,  tractors,  etc.,  should
      not  be allowed on  the  geomembrane  unless  otherwise  specified  by the
      manufacturer  and approved in the CQA/CQC  Documents.

(e)    The  two geomembrane sheets to be joined must  be properly positioned
      so that approximately  15 cm (6 inches) of overlap exists.   If the
      overlap is insufficient,  lift the  geomembrane sheet  up  and down to
      allow air to  be pumped beneath it  and  "float" it into  proper
      position.

(f)    If the overlap is  excessive,  the excess material may be trimmed with
      scissors or worked away from the edges of the seam  to  maintain
      proper overlap, as shown in Figure 9.1(a-b).   All cut  scrim edges
      must be sealed with a  flood coat of  bodied chemical  or  the
      manufacturer's/fabricator's approved liquid sealant.

(g)    When reinforced geomembranes are cut to accommodate  odd shapes or to
      fit  small pieces,  resealing of the exposed scrim by  flood coating is
      required by the use of manufacturer's  or  fabricator's  approved
      liquid sealant. This  sealant is usually  a thickened chemical  of the
      same type used to  do the production  field seaming.

(h)    All  cutting and preparation of odd shaped sections  or  small fitted
      pieces can be accomplished at the  discretion  of the  installer so
      that production field  seaming can  be completed with  as  few
      interruptions as possible.

(i)    The  two opposing geomembrane sheets  to be joined should be visually
      checked for defects of sufficient  magnitude to effect  seam quality.
      The  criteria  to be met and the procedures to  be used in this  regard
      should be stipulated in the contract specifications  and/or in the
      CQC/CQA Documents.

(j)    If the construction plans require  overlaps to be shingled in  a
      particular direction,  this should  be checked.

(k)    Excessive undulations  (waves) along  the seams during the seaming
      operation should be avoided.   When this occurs due  to  either  the
      upper or lower sheet having more slack than the other  or because of
      thermal expansion  and  contraction, it  often leads to the undesirable
      formation of  "fishmouths" which must be trimmed, laid  flat and
      reseamed with a patch.  An example of  a fishmouth and  its correction
      is shown in Figure 9.2(a-c).

(1)    There should  be some slack in the  installed liner which depends on
      the  type of geomembrane,  the ambient and  anticipated service
      temperatures,  length of time the geomembrane  will be exposed,
      location of the facility, etc.   This is a design consideration and
      the  plans and specifications must  be project  specific  on the  amount
      and  orientation of this slack.
                                 110

-------
Figure
Commended for




 111
                                                cutting of geomembranes.

-------
Figure 9.2(a).   Formation of "fishmouth"  resulting  from  excessive  slack
                in upper geomembrane versus  lower geomembrane.
       Figure  9.2(b).   Cutting of  "fishmouth" along  its centerline.


                                   112

-------
Figure 9.2(c).   Patch over the entire area where "Fishmouth"  was located.
  (m)   The sheets which are overlapped for seaming  must be clean.   If
        dirty,  they must be cleaned with dry rags.   If processing aids were
        used in the manufacture of the sheet,  this must be removed.

  (n)   The sheets which are overlapped for seaming  must be free of  moisture
        in the  seam area.

  (o)   Seaming is not allowed during rain or snow,  unless proper
        precautions are made to allow the seam to be made with dry
        geomembrane sheets, e.g.,  within an enclosure or shelter.

  (p)   It is preferable not to have water saturated soil beneath the
        geomembrane during installation.  Seaming boards help in this regard
        by lifting the seams off the soil subgrade.

  (q)   If the  soil beneath the geomembrane is frozen, the heat from hot air
        guns or any preheating lamps that may be used can thaw the frost
        allowing water to be condensed onto the unbonded region ahead of the
        seam being fabricated.  This possibility may be eliminated by the
        use of  suitable seaming boards or slip sheets made from excess
        geomembrane.

  (r)   Sheet temperatures for seaming should be above freezing, i.e. O'C
        (32F)  unless it can be proven with test strips that good seams
        can be  fabricated at lower temperatures.  However, temperature is of
        less concern to good seam quality than is moisture.

                                   113

-------
I
     (s)   For cold weather seaming,  it may be advisable to preheat the sheets
           with a radiant heater, or hot air blower,  or to use a tent of some
           sort to prevent heat losses during seaming and to make numerous test
           seams in order to determine appropriate seaming conditions.

     (t)   Sheet temperatures for seaming should be below 50C (122F)  as
           measured by an infrared thermometer or a surface contact
           thermocouple.  It is recognized that depending on material type and
           thickness, higher temperatures may be allowed.  It should also be
           recognized that wind and cloud cover will  determine the actual sheet
           temperature.  High temperatures affect not only worker performance,
           but may also affect seam durability of some geomembranes unless
           special precautions are taken.  For temperatures above this value
           special attention should be paid to the seaming, frequent test
           strips and more diligent non destructive testing is recommended.
           NOTE:  For items (q), (r), (s,) and (t) the CQC/CQA Documents
           and/or project specifications and the regulatory requirements
           regarding hot and cold temperature seaming limitations should be
           reviewed to avoid possible problems with final construction
           certification acceptance.


9.2  EQUIPMENT PREPARATION

     (a)   An ample supply of the appropriate fusion  chemicals must be
           available at the job site.  They should be stored at room
           temperature and sheltered from the elements.  Storage is to be away
           from any portion of the geomembrane so that accidental spillage can
           not occur on the liner itself, or over a diked retaining pad or
           impoundment, so that chemicals cannot penetrate the ground.  The
           listed shelf life of the fusion chemical shall not be exceeded.
           Fusion chemicals that have been left open  and started to solidify
           should not be remixed or used.

     (b)   An ample supply of plastic applicator bottles (or other suitable
           applicators) with special  end applicators  should be available.  Note
           that the filling of these applicator bottles is to take place away
           from the geomembrane area.  See Figure 9.3 for the typical type of
           applicator bottles and their use in applying the fusion chemicals.

     (c)   A 5 cm to 10 cm (2 to 4 inches) wide paint brush may be used to
           apply bodied chemical to the area to be seamed.  The bristles should
           be made from materials which do not react  with the chemical being
           applied.

     (d)   Clean, dry rags and or sponges will be needed to clean the sheet
           areas to be seamed as well as to wipe away excess chemical from the
           seamed area after the seam is completed.  These rags should be
           chemically resistant to the bonding liquid.  Lint-free natural fiber
           rags made of cotton or wool are generally recommended.
                                             114

-------
Figure 9.3.   Photograph of applicator bottles and method of application.


  (e)   Pressure applicators including rollers, either steel, rubber, nylon
       or wood depending on site specific conditions, from 5 to 9 cm (2 to
       3 1/2 inches) wide, will be needed for applying pressure to the
       bonded area after the fusion chemical has been applied.  Figure  9.4
       illustrates the types of rollers in common use.  Pressure applied
       with a rag or wood paddle has been successfully used in place of a
       roller to achieve a good seam.

  (f)   Seaming boards or slip sheets should be available.  They need to be
       rigid enough to provide adequate resistive force for seaming
       pressures.  The seaming boards must be smooth with rounded corners
       and edges and have a hole drilled at one end for attaching a pull
       rope.  If needed, they may serve as temporary working platforms
       placed beneath the seaming area to provide a smooth surface and  a
       base for physical resistance to the applied pressure of the rollers.
       They also provide insulation to heat and help keep dirt and moisture
       away from the seaming area.

  (g)   Hot air guns or other appropriate heating devices are necessary to
       heat the geomembrane when performing cold-temperature field seaming.

  (h)   For cold-temperature seaming, properly functioning electric
       generators to power the heating devices or heat guns, must be
       available within close proximity of the seaming region and with
       adequate extension cords to complete the entire seam.  These
       generators should be of sufficient size or numbers to handle all
       seaming and preheating electrical requirements.  The generator must
       have rubber tires, or be placed on a smooth plate such that it is
                                  115

-------
          Figure 9.4.  Photograph of types of rollers used to apply
                       pressure to chemically bonded seams.


           completely stable in order that it will not damage the geomembrane.
           Fuel (gasoline or diesel) for the generator must be stored away from
           the geomembrane and if accidently spilled on the geomembrane must be
           immediately removed.  The area should be inspected for damage to the
           geomembrane and repaired if necessary.


9.3  TEST STRIPS

     A general requirement of most CQA Documents is that "test seams" or "test
strips" be made on a periodic basis.  Test strips generally reflect the quality
of field seams but should never be used solely for final field seam acceptance.
Final field seam acceptance should be specified in the contract specification
and should include a minimum level of destructive testing of the production
field seams.   Test strips are made to minimize the amount of destructive
sampling/testing which requires subsequent repair of the final field seam.
Typically these test seams, for each seaming crew, are made about every four
hours, or every time equipment is changed, or if significant changes in
geomembrane temperature are observed, or as required in the contract
specification.  This is a recommended practice that should be followed when
seaming all types of geomembranes.  The purpose of these tests is to establish
that proper seaming materials, temperatures, pressures, rates, and techniques
along with the necessary geomembrane pre-seaming preparation is being
accomplished.   Test strips may be used for CQA/CQC evaluation, archiving, for
exposure tests, etc., and must be of sufficient length to satisfy these various
needs.

                                      116

-------
     Each seaming crew and the materials they are using must be traceable and
identifiable to their test seams.  While the test seams are being prepared,
cured, and CQC tested, the seaming crew may continue to worx as long as the
seams they have made (and are making) since their last acceptable test sample
strip was prepared, are completely traceable and identifiable.  If a test seam
fails to meet the field seam design specification, then an additional test seam
sample will have to be made by the same seaming crew - using the same tools,
equipment and seaming materials - and retested.

     The liner's finished field seams will not be accepted unless the before
and after "test seam sample strip" CQC test results (or other CQC seam test
result criteria as required per the design specification) are acceptable per
the site's design specifications.  If a seam is not accepted, destructive
testing of samples from the actual seam will be removed from the liner and
tested.  If the actual seam destructive test results still do not meet the
design specification requirement, then the unacceptable seams will all have to
be repaired or reconstructed with seaming materials by a test proven seaming
crew that has passed its testing requirements.  The procedure illustrated in
the flow chart of Figure 9.5 must be followed.  Note that the failure of test
strip 1 requires two actions:  (a) the making of test strip 2, and (b) an
increased frequency of destructive tests on production field seams made during
the curing of test strip 1 (if any were made).  This increased frequency must
be stipulated in the contract specifications or in the CQC/CQA Documents.

     If the destructive seams fail or if test strip 2 fails, production field
seaming is halted.  All production field seams made during the interval are
repaired per the contract specifications or CQC/CQA Documents to the point of
previous acceptance with an approved seaming crew.

     At this point, the seaming crew that failed to pass both strip tests must
adjust and recertify current seaming equipment and technique or obtain new
seaming equipment, tools and/or retrain personnel and begin making initial test
strip samples.

     For chemical fusion seams or bodied chemical fusion seams, test strips of
the type shown in Figure 9.6(a-d) are prepared as required by the contract
specification or CQC/CQA Documents.  The seam is centered lengthwise between
the two sheets to be joined.  Figure 9.6(a) shows the two geomembrane pieces to
be seamed being cleaned and properly aligned, 9.6(b) shows the chemical being
applied to bonding area, 9.6(c) shows the completed seam being smoothed and
rolled, 9.6(d) shows samples being cut from completed test strips for
subsequent destructive testing.

     For geomembranes that are seamed by chemical fusion methods, on site CQC
testing requires time that, without accelerated curing, can range from a few
hours to days.  Accelerated curing of seam test samples using an oven on site,
or another suitable heat source, can be accomplished at temperature ranges
between 50C (122"F) and 70C (158F) within periods that range from 1 hour to
16 hours, dependent upon the following variables: material type, thickness,
chemical fusion system, seam width, etc.  After the accelerated curing period
the samples are allowed to cool at least 1/2 hour prior to CQC peel and shear

                                      117

-------
                      'Not*: S**mlng CnwFilling to Pnptn
                       Accipttt/f nastriptlliyfiK/u/n
                       Rttnlning InAcconltncf with CQC/C04. Document*
Figure  9.5.   Test strip  process  flow chart.

                         118

-------
      Figure 9.6(a).   Alignment of test strip and  cleaning of area to
                      be bonded.
Figure 9.6(b).  Applying fusion chemical  to area of lower geomembrane
                to be bonded.

                                  119

-------
                      Figure 9.6(c).  Smoothing and rolling bonded area.
I
             Figure  9.6(d).   Cutting  the  test  strip  samples  for  appropriate
                             groups for testing  or storage.
                                              120

-------
testing.  Volatile chemical odors should no longer be detected.  The exact
procedures should be specifically written into the CQC/CQA Documents.

     During the CQC and CQA test requirement periods, a liner should not be
covered and it cannot be placed into service.  This will  insure the ease of
repairing or reconstructing in the event it is required.   During this period it
is imperative that the liner be properly ballasted and otherwise secured so as
to prevent wind or unusual weather damage.


9.4  ACTUAL SEAMING PROCESS

     (a)   Position the geomembrane panels  so that the entire length of the
           seam area overlaps.  If required for site specific considerations,
           place the desired length of seaming board or slip sheet beneath the
           seam and correctly position it so as to provide a good working
           surface for the area to be seamed, see Figure 9.7.

     (b)   Use a fine bristle brush, clean  rags,  or other means to remove soil
           particles or dust from the area  to be  seamed.

     (c)   If two seaming crews can work simultaneously on the same seam, begin
           seaming at the mid-point of the  geomembrane panels and work toward
           the ends.  This tends to prevent fishmouths occurring in the center
           of the panel.  On slopes, seaming should proceed uphill.

     (d)   In constructing field seams one  invariably encounters areas where
           three thicknesses of material  need to  be bonded together.  These
           areas occur at the intersection  of factory and field seams and are
           known as "T" connections, see Figure 9.8 for schematic
           representation of the "T" connection.   Either additional fusion
           chemical should be used in these areas to bond the loose flap or the
           loose portion of the flap should be trimmed off.

     (e)   A "T" trimming tool in action is pictured in Figure 9.9 showing the
           trimming of the flap in the lower geomembrane.   The "T" trimming
           tool  resembles a cheese cutter with a  replaceable razor blade
           cutting edge.  It is only used to trim nonreinforced geomembranes
           like  PVC or unreinforced CSPE and CPE  and then only for geomembranes
           greater than 0.75 mm (30 mils).

           For reinforced geomembranes one  should discourage this type of
           trimming because it exposes the  scrim  reinforcement.  Such exposed
           scrim should be avoided since moisture and/or leachate could wick up
           the scrim and cause delamination or other undesirable effects.
           Reinforced geomembranes should be trimmed as accurately as possible
           with  a razor hook knife,  with a  backing to prevent damage to the
           underlying geomembrane.  In all  locations where the ends of scrim
           are exposed one should use bodied adhesive chemicals or sealants
           which,  due to their higher viscosity,  can be more generously applied
           (called "flood coating")  in these regions.   All  exposed scrim should
           be sealed.

                                      121

-------
 Rope for I
advancing)*
 seaming
 board




fck^

j\
t
s
' ^  Upper Geomembrane 	 A
' Edge of Lower Geomembrane
'>x;

/
' ^
.50 mm (2 in.) Unbonded Overlap
k 100 mm (4 in.)
50 mm (2 in.) Seam Width Overlap Width
 X/ // // // // //y^
>v I
250 mm
Seaming
^/l
\ 	 i



(10 in.)
Board

                  Edge of Upper Geomembrane

                          ^~- Lower Geomembrane 
                                       Direction of Seaming
                             bonded	.          ^ unbonded
                                      .50 mm .50 mm
                                                       Upper Geomembrane
(2 in.)
                 Lower Geomembrane
                                         Section A-A
                                                      Seaming Board
      Figure 9.7.   Positioning  of wooden "seaming board" beneath seam
                    area of liner to provide  for  a uniform and  smooth
                    subsurface.
                                       122

-------
Factory Seams (previously made)
           ^^


     Panel "A"

       /
                                                               Field Seam
                                                               (to be made)
                                   Field Seam "V-ower Edge
                                               of Panel
Figure 9.8.  Perspective  diagram of locations where "T"  configurations
             commonly  occur.
    Figure 9.9.  Photograph  of "T"  trimming tool shaving the  upper
                 surface  of  an existing seam in preparation of new
                 intersecting  seam.
                                    123

-------
(f)   The appropriate fusion chemical  is applied with an applicator
      (squeeze botle or brush)  until  it completely wets the bottom
      geomembrane.   Care must be taken to make sure that enough fusion
      chemical is applied to wet and  fuse both surfaces that are being
      seamed.   This adequate coverage  can be seen since properly wetted
      areas appear different than non-wetted areas.  Any excess fusion
      chemical should be wiped  up quickly to prevent puddling,  which could
      damage the geomembrane, see Figure 9.10.

(g)   After applying the fusion chemical, an "initial reaction" time, or
      "dwell"  time is required  for the chemical  to soften the surface of
      the geomembrane sheet.  Dwell times for various thicknesses of
      different geomembranes are from  2 to 5 seconds.  Note that high
      ambient  temperatures,  strong wind, and low relative humidity all
      tend to  reduce the time necessary for the  fusion chemical to soften
      the surface of the sheet.  Therefore, if these conditions exist, the
      "dwell time"  will be decreased.   The determination of dwell time
      emphasizes the importance of the preparation and testing  of test
      strips which were described earlier.

(h)   Following the dwell time, the two liner surfaces are mated together
      and pressure is applied to the upper surface.  The pressure is
      applied  with  a roller or  other suitable pressure device.  The process
      involves rolling the seam both  in a parallel and a perpendicular or
      45 degree direction so as to mate and fuse the two liner  surfaces,
      remove air pockets, and to force any excess fusion chemical toward
      and out  of the exposed overlap edge.  The  seaming technician should
      make a sufficient number  of passes with the roller to insure that
      both surface mating and excess chemical removal has been
      accomplished.  Generally  between 5-10 passes in each direction over
      a 60 cm  (2 ft.) length will be needed, see Figure 9.11(a-b).
      However, the use of any alternative chemical or pressure  applicators
      must be  evaluated with test strip seams.

(i)   Rolling  should be accomplished using uniform pressure in  a flowing
      motion.   This will lead to an acceptable seam with no entrapped
      vapor or air pockets.   Excessive pressure, e.g. pressure  that would
      cause the material to indent or  crease, is not required.

(j)   After applying pressure to a section of seam, any excess  fusion
      chemical should be wiped  off the top of the geomembrane.   Wipe
      toward the leading edge of the seam not away from it.  For
      reinforced geomembranes it is desirable to see a small bead of
      fusion chemical extend to the outer edge of the seam.

(k)   Clean pressure applicators should be used  at all times.  When a
      roller is used, a clean surface  must be maintained.
                                 124

-------
      Figure 9.10.  Application of fusion chemical.

^ x

^
\

\
^
. Upper Geomembrane
> 50 nV72 in> N N N \ \ \
'UnbondedtiLZona .... ...
^ T c

Seam iZone ' t

(finish^
1 Approximately 60 cm
^ 	 Lower Geomembrane 	
Edge of Lower
J Geomembrane
\ N \ X\NV
(start) 100 mm (4 in.)
*~ } Overlap Zone
^ 5 passes
/ s I/ / /\t/
, 1^
(2 ft)l \EdgeofUpper
Geomembrane
Figure 9.11(a).  Parallel  rolling motion for the fabrication
                 of chemically fused seams.

                           125

-------
             /SO mm (2 in.)
                 Seam I Zone
                               pproximately 60 cm (2 ft.]
               8 passes

   Lower Geomembrane
                                                            Edge of Lower
                                                            Geomembrane
                                                               100 mm (4 in.)
                                                               Overlap Zone
                                                             Edge of Upper
                                                             Geomembrane
     Figure 9.11(b).
Perpendicular rolling motion for the fabrication
of chemically fused seams.
9.5  AFTER SEAMING

    (a)   The seam must be checked visually for uniformity of width and
          surface continuity.  As stated earlier, proper fusion chemical
          application visually changes the surface appearance.  Usually the
          installer will use an air lance or blunt-end pick, see Figure
          9.12(a-b), to check for voids or gaps under the overlapping
          geomembrane.

    (b)   When unbonded areas are located, they can sometimes be repaired
          by inserting more bonding agent into the opening and applying
          pressure.  If that is not satisfactory, a patch must be placed
          over them with at least 15 cm (6 inches) of geomembrane extending
          on all sides.

    (c)   Any area of the geomembrane sheets where fusion chemical
          accidentally spilled and caused damage greater than 10% of the
          original thickness, must be patched as above, with at least  15
          cm(6 inches) of geomembrane extending beyond the affected areas.

    (d)   Any area of the geomembrane sheets where puncture holes are
          observed must be patched as above, with at least 15 cm (6 inches)
          of geomembrane extending beyond the affected areas.
                                    126

-------
         (a)  Air  lance  test.
                                                  (b) Pick test.
Figure 9
.12.   Photographs  of  air  lance  and pick testing of completed sea..



                           127

-------
    (e)   Note that with the above three repair items (b,  c, and d) it is
          not practical to use a seaming board beneath the geomembrane.
          However, a piece of the liner material  can be used for added
          support under the liner, if needed, even if the  hole must be
          enlarged to insert the piece before the patch is made.  This
          added piece is left there indefinitely.  In either situation,
          additional care should be used to insure a proper bond.

    (f)   At the completion of seaming, all rags, chemical containers,
          etc., should be properly removed from the geomembrane.

    (g)   Sand bags used to resist wind uplift stresses may be placed on
          the seamed areas in accordance with customary installation
          practice, as prescribed in the contract specifications, or
          CQC/CQA Documents.

    (h)   Cross sections of the completed seams are shown  in Figure
          9.13(a-c).
9.6 UNUSUAL CONDITIONS

    This section is written to give insight into conditions which go
beyond the general description just presented.

    (a)   High winds, or gusts of wind,  are always problematic for liners.
          After deploying the geomembrane,  the  panels should be adequately
          ballasted, e.g., with sandbags.   The  actual seaming operation,
          however, may require the removal  of some of the ballast leaving
          the windward edge vulnerable to  wind  uplift forces.  If
          possible, proper orientation of  the overlap might be helpful.
          Otherwise, additional labor may  be required to only remove
          sandbags immediately in front of the  seaming operation.  The
          liner must be cleaned of any dirt and moisture left behind after
          sandbag removal.  They are then  to be replaced behind the
          completed seaming operation.

    (b)   Patches are invariably necessary to make at locations where
          destructive test samples are removed  or where seams are shown to
          fail nondestructive testing.  These patches must extend a
          minimum of 15 cm (6 inches) beyond the outer limits of the area
          to be repaired.  Since a seaming board cannot be used in these
          areas, additional care is necessary.   Sometimes excess pieces of
          geomembrane material, which are  left  in place, are positioned
          beneath the area to be seamed.
                                    128

-------
 Figure  9.13(a).   Cross  sections  of  PVC  liner  seams  prepared  by
                  the  chemical  fusion method showing left  side of
                  completed  seam.
Figure 9.13(b).
Cross sections of PVC liner seams prepared by the
chemical fusion method showing center of completed
seam.
                               129

-------
 Figure 9.13(c).
Cross sections of PVC liner seams prepared
by the chemical fusion method showing right
side of completed seam.
(c)    Details around sumps,  pipes and other appurtenances are perhaps
      the most demanding locations to properly seam in  an entire
      facility.  Also due to their typical  locations being at low
      points of the containment facility's  design,  these areas
      inherently operate under larger hydraulic heads.   Should a
      defect from improper seaming occur in such a  location leakage
      rates and its associated adverse impacts are  heightened.
      Therefore, extreme care should be exercised in ensuring seam
      integrity in these often difficult to reach locations.   The
      fusion chemical should be placed symmetrically on both liners to
      be joined which may be difficult for  external and internal edges
      and particularly at corners.  Hand and finger pressure may be
      needed in tight areas.

(d)    This section was written for material temperatures that range
      between 0"C (32'F) and 50C (122F).   This is the temperature
      range that is generally recognized as being acceptable for
      seaming without taking special precautions.

      For sheet temperatures below 0C (32F), shielding, pre-heating,
      different chemical compounds and/or a slower  seaming rate may be
      required.  More frequent seam testing and precautions to prevent
      thawing subgrade (previously discussed) may have  to be taken.
      Sharp, frozen subgrade should be avoided to eliminate point
      pressure damage potential.

      For sheet temperatures above 50C (122F) shielding and rate of
      seaming should be adjusted.  More frequent destructive seam
      testing may have to be taken.
                               130

-------
FIELD NOTES:
                                   131

-------
FIELD NOTES:
                                      132

-------
                                  SECTION 10

                      DETAILS OF CHEMICAL ADHESIVE SEAMS


     As is shown in Table 4.2, chemical adhesive seaming represents an
applicable field seaming method for PVC, CPE, EIA, CSPE liners, both
reinforced and unreinforced.  Adhesives differ from other bonding agents in
that they necessarily contain materials that are dissimilar to the liner
material itself.  In addition to seaming adhesives, they are also sometimes
used to seal exposed fabric or scrim.  This section focuses only on the use of
adhesives for seaming compounded thermoplastic and thermoplastic elastomeric
geomembranes.

10.1  GEOMEMBRANE PREPARATION

     (a)   Note that this document assumes that the proper geomembrane has
           been visually inspected to ensure it is free of deep scratches or
           defects that would cause the sheet to not meet the specifications
           of the installation.  It is further assumed the sheet has been
           delivered to the site and brought to its approximate plan position
           (as per design the panel layout) for final installation and
           seaming.  Only the material that can be seamed that day should be
           deployed.  All deployed material should be ballasted immediately to
           prevent wind uplift.

     (b)   The geomembrane will usually arrive on site in the form of
           prefabricated panels which are accordion-folded in both directions.
           These panels are usually packaged in palletized, heavy weatherable
           cardboard containers.

     (c)   The geomembrane should remain packaged and dry until ready for use.
           The material should not be unfolded when material temperatures are
           lower than -10"C (14F) due to the possibility of cracking.  If the
           panel is stored in a warm place, e.g. 10C (50'F) or above, prior
           to being unfolded or unrolled on site, then it can be placed at
           -18"C (0F) or below temperatures providing the time between
           removing the geomembrane from storage and deployment does not
           exceed one-half working day.  Geomembrane deployment may be allowed
           for other conditions but the CQC/CQA Documents must be specific as
           to the conditions.

     (d)   All personnel walking on the geomembrane should have smooth soled
           shoes.  Heavy equipment, e.g. pickups, tractors, etc., should not
           be allowed on the geomembrane at any time, unless otherwise
           specified by the manufacturer and approved in the CQC/CQA
           Documents.

                                      133

-------
(e)    The two geomembrane sheets to be joined  must be properly positioned
      such that approximately 15 cm (6 inches) of overlap exists.   If the
      overlap is insufficient,  lift the geomembrane sheet up and down to
      allow air to be pumped beneath it and "float" it into proper
      position.

(f)    If the overlap is excessive,  the excess  material may be trimmed
      with scissors or worked away  from the edges of the seam to maintain
      proper overlap, as shown  in Figure 10.1  (a-b).   All  cut scrim edges
      must be sealed with a flood coat of bodied  adhesive or the
      manufacturer's/fabricator's approved liquid sealant.

(g)    When reinforced geomembranes  are cut to  accommodate odd shapes or
      to fit small pieces,  resealing of the exposed scrim by flood
      coating is required by the use of manufacturer's or fabricators
      approved liquid adhesive.   This adhesive is usually a thickened
      chemical of the same type used to do the production seaming as
      described in Section 9.

(h)    All cutting and preparation of odd shaped sections or small  fitted
      pieces can be accomplished at the discretion of the installer so
      that production field seaming can be completed with as few
      interruptions as possible.

(i)    The two opposing geomembrane  sheets to be joined should be visually
      checked for defects of sufficient magnitude to affect seam quality.
      The criteria to be met and the procedures to be used in this regard
      should be stipulated in the contract specifications and/or in the
      CQC/CQA Documents.

(j)    If the construction plan  requires overlaps  to be shingled in a
      particular direction, this should be checked.

(k)    Excessive undulations (waves) along the  seams during the seaming
      operation should be avoided.   When this  occurs due to either the
      upper or lower sheet having more slack than the other or because of
      thermal expansion and contraction, it often leads to the
      undesirable formation of  "fishmouths" which must be trimmed, laid
      flat and reseamed with a  patch.  An example of a fishmouth and its
      correction is shown in Figure 10.2.(a-d).

(1)    There should be some slack in the installed liner which depends on
      the type of geomembrane,  the  ambient and anticipated service
      temperatures, length of time  the geomembrane will be exposed,
      location of the facility,  etc.  This is  a design consideration and
      the plans and specifications  must be project specific on the amount
      and orientation of this slack.

(m)    The sheets which are overlapped for seaming must be clean.  If
      dirty, they must be wiped clean with dry rags.   If processing aids
      were used in the manufacture  of the sheet,  this must be removed.
                                134

-------
Figure 10.1(a).   Trimming of excess geomembrane sheet to obtain proper
                 overlap prior to seaming.
   Figure 10.1(b).   Type of scissors recommended for cutting of
                    geomembrane sheets.
                                 135

-------
Figure 10.2(a).   Formation of "fishmouth"  resulting  from excessive
                 slack in upper geomembrane  versus lower geomembram
   Figure 10.2(b).  Cutting of "fishmouth" along its centerline
                                136

-------
      Figure  10.2(c).
Overlapping and seaming the ends of the upper
geomembrane to the lower geomembrane.
Figure 10.2(d).   Patch over the entire  area where  "fishmouth"  was  located.
                                   137

-------
(n)    The sheets which are overlapped for seaming  must  be completely free
      of moisture in the seam area.

(o)    Seaming is not allowed during  rain or snow,  unless proper
      precautions are made to allow  the seam to  be made on dry
      geomembrane sheets,  e.g.,  within an enclosure or  shelter.

(p)    It is preferable not to have water-saturated soil beneath the
      geomembrane during installation.  Seaming  boards  help in this
      regard by lifting the seams off the soil  subgrade.

(q)    If the soil beneath the geomembrane is frozen,  the heat from hot
      air guns and radiant lamps can thaw the frost allowing water to be
      condensed onto the unbonded region ahead  of  the seam being
      fabricated.  This possibility  may be eliminated by the use of
      suitable seaming boards or slip sheets made  from the excess
      geomembrane.

(r)    Ambient temperatures for seaming should be above freezing, i.e.
      O'C (32F), unless it can  be proven with  test strips that good
      seams can be fabricated at lower temperatures.   However,
      temperature is of less concern to good seam  quality than is
      moisture.

(s)    For cold weather seaming,  it may be advisable to preheat the sheets
      with a radiant heater, hot air blower, or to use a tent of some
      sort to prevent heat losses during seaming and to make numerous
      test seams in order to determine appropriate seaming conditions.

(t)    Sheet temperatures for seaming should be below 50C (122'F)as
      measured by an infrared thermometer or surface contact
      thermocouple.  It is recognized that depending on material type and
      thickness, higher temperatures may be allowed.  It should also be
      recognized that wind and cloud cover will  determine the actual
      sheet temperature.  High temperatures affect not only worker
      performance, but may also affect seam durability of some
      geomembranes unless special precautions are taken.  For
      temperatures above this value  special attention should be paid to
      the seaming, frequent test strips and more diligent nondestructive
      testing  is recommended.
      NOTE:  For items (q), (r), (s,) and (t) the CQC/CQA Documents
      and/or project specifications  and the regulatory requirements
      regarding hot and cold temperature seaming limitations should be
      reviewed to avoid possible problems with final  construction
      certification acceptance.


10.2  EQUIPMENT PREPARATION

(a)   An ample supply of the appropriate adhesive must be available at
      the job  site.   It should be stored at room temperature and
      sheltered from the elements.  Chemical adhesives that have been

                                 138

-------
      left open and started to solidify should not be remixed or used.
      Storage is to be away from any portion of the geomembrane so that
      accidental spillage can not occur on the liner itself or over a
      diked retaining pad or impoundment,  so that chemicals cannot
      penetrate the ground.  The listed shelf life cannot be exceeded.

(b)    A 5 cm to 10 cm (2 to 4 inches) wide paint brush will be needed to
      apply adhesive to the area to be bonded.  The bristles must be made
      from materials which are not softened or dissolved by the adhesive.

(c)    At least one clean paint can of a minimum capacity of 1/4 1 (1 pt.)
      will be needed by each seaming crew.  The can should only be filled
      one third full to avoid spillage during the seaming process.

(d)    A soft bristled brush and numerous rags will  be needed to clean the
      geomembrane to be seamed as well as  wipe away any excess adhesive
      after seaming.  The brush and rags should be chemically resistant
      to the adhesive.

(e)    Pressure applicators including rollers, either steel, rubber,  nylon
      or wood depending on site specific conditions, from 5 to 9 cm (2 to
      3-1/2 inches) wide, will be needed for applying pressure to the
      bonded area after the adhesive has been applied.  Figure 10.3
      illustrates the types of rollers in  common use.  Pressure applied
      with a rag or wood paddle has been successfully used in place of a
      roller to achieve a good seam.
       Figure  10.3.   Photograph  of types  of  rollers  used  to
                     apply  pressure to  solvent  adhesive seams.

                                139

-------
      (f)   An ample supply of adhesive resistant gloves will be necessary to
            eliminate the possibility of the adhesive coming in contact with
            the skin.

      (g)   Seaming boards made from wooden planks or slip sheets should be
            available.  The seaming boards must be smooth with rounded corners
            and edges and have a hole drilled at one end for attaching a pull
            rope.  If needed, they may serve as temporary working platforms
            placed beneath the seaming area to provide a smooth surface and a
            base for physical resistance to the applied pressure of the
            rollers.  They also provide insulation to heat and help keep dirt
            and moisture away from the seaming area.

      (h)   Hot air guns or other appropriate heating devices are necessary to
            heat the geomembrane when performing cold temperature field
            seaming.

      (i)   For cold temperature seaming, properly functioning electric
            generators to power the heating devices or heat guns, must be
            available within close proximity of the seaming region and with
            adequate extension cords to complete the entire seam.  These
            generators should be of sufficient size or numbers to handle all
            seaming electrical requirements.  The generator must have rubber
            tires, or be placed on a smooth plate such that it is completely
            stable in order that it will not damage the geomembrane.  Fuel
            (gasoline or diesel) for the generator must be stored away from
            the geomembrane and if accidently spilled on the geomembrane must
            be immediately removed.  The area should be inspected for damage
            to the geomembrane and repaired if necessary.


10.3  TEST STRIPS

     A general requirement of most CQA Documents is that "test seams" or "test
strips" be made on a periodic basis.  Test strips generally reflect the
quality of field seams but should never be used solely for final field seam
acceptance.  Final field seam acceptance should be specified in the contract
specification and should include a minimum level of destructive testing of the
production field seams.  Test strips are made to minimize the amount of
destructive sampling/testing which requires subsequent repair of the final
field seam.  Typically these test seams, for each seaming crew, are made about
every four hours, or every time equipment is changed, or if significant
changes in geomembrane temperature are observed, or as required in the
contract specification.  This is a recommended practice that should be
followed when seaming all types of geomembranes.  The purpose of these tests
is to establish that proper seaming materials, temperatures, pressures, rates,
and techniques along with the necessary geomembrane pre-seaming preparation is
being accomplished.  Test strips may be used for CQA/CQC evaluation,
archiving, for exposure tests, etc., and must be of sufficient length to
satisfy these various needs.
                                      140

-------
     Each seaming crew and the materials they are using must be traceable and
identifiable to their test seams.  While the test seams are being prepared,
cured, and CQC tested, the seaming crew may continue to work as long as the
seams they have made (and are making) since their last acceptable test sample
strip was prepared, are completely traceable and identifiable.  If a test seam
fails to meet the field seam design specification, then an additional test
seam sample will have to be made by the same seaming crew - using the same
tools, equipment and seaming materials - and retested.

     The liner's finished field seams will not be accepted unless the before
and after "test seam sample strip" CQC test results (or other CQC seam test
result criteria as required per the design specification) are acceptable per
the site's design specifications.  If a seam is not accepted, destructive
testing of samples from the actual seam will be removed from the liner and
tested.  If the actual seam destructive test results still do not meet the
design specification requirement, then the unacceptable seams will all have to
be repaired or reconstructed with seaming materials by a test proven seaming
crew that has passed its testing requirements.  The procedure illustrated in
the flow chart of Figure 10.4. must be followed.  Note that the failure of
test strip 1 requires two actions:  (a) the making of test strip 2, and (b) an
increased frequency of destructive tests on production field seams made during
the curing of test strip 1 (if any were made).  This increased frequency must
be stipulated in the contract specifications or in the CQC/CQA Documents.

     If the destructive seams fail or if test strip 2 fails, production field
seaming is halted.  All production field seams made during the interval are
repaired per the contract specifications or CQC/CQA Documents to the point of
previous acceptance with an approved seaming crew.

     At this point, the seaming crew that failed to pass both strip tests must
adjust and recertify current seaming equipment and technique or obtain new
seaming equipment, tools and/or retrain personnel and begin making initial
test strip samples.

     For adhesive seams, test strips of the type shown in Figure 10.5(a-e) are
prepared.  The seam is centered lengthwise between the two sheets to be
joined.  Figure 10.5 (a) shows the two geomembrane pieces to be seamed being
cleaned and properly aligned, 10.5 (b) shows chemical  adhesive being applied
to bonding area, 10.5 (c) shows adhesive in "tack" stage, 10.5 (d) shows
samples being cut from completed test strips for subsequent destructive
testing and 10.5 (e) shows the individual  samples cut from the test strip
being identified.

     For geomembranes that are seamed by adhesive methods, on site CQC testing
requires time that, without accelerated curing,  can range from a few hours to
days.   Accelerated curing of seam test samples using an oven on site,  or
another suitable heat source, can be accomplished at temperature ranges
between 50'C (122*F) and 70C (158'F)  within periods that range from 1 hour to
16 hours, dependent upon the following variables: material type,  thickness,
adhesive system, seam width,  etc.   After the accelerated curing period the
samples are allowed to cool  at least 1/2 hour prior to peel  and tensile/shear


                                      141

-------
                        'Hoi*: Sttmlng CnwFMng to Pnptn
                         Accipttblt Tut Strip* MtyRtquIn
                         Kttnlnlng IttAccordtnct wHh CQC/CQA Doamntt
Figure  10.4.   Test  strip process  flow chart.

                         142

-------
Figure 10.5(a). (Upper Left)  Alignment of test strip and cleaning of area to
                              be area to be bonded.

Figure 10.5(b). (Lower Right) Applying chemical adhesive to area of lower
                              geomembrane to be bonded.

                                      143

-------
        Figure  10.5(c).  Adhesive  in the "tack" stage.
Figure 10.5 (d).   Cutting samples from completed test strips.
                             144

-------
        Figure 10.5(e).
Marking the test strip samples for appropriate
groups for testing or storage.
testing.  Volatile chemical odor should no longer be detected.   The exact
procedure should be specifically written into the CQC/CQA Documents.

     During the CQC and CQA test requirement periods, a liner should not be
covered and it cannot be placed into service.  This will  insure the ease of
repairing and reconstructing in the event it is required.  During this period
it is imperative that the liner be properly ballasted and otherwise secured so
as to prevent wind or unusual  weather damage.
10.4  ACTUAL SEAMING PROCESS

     (a)   Position the geomembrane panels so that the entire length of the
           seam area overlaps.   If required for site specific considerations,
           place the desired length of seaming board or slip sheet beneath the
           seam and correctly position it so as to provide a good working
           surface for the area to be seamed, see Figure 10.6.

      (b)    Use a fine bristle  brush or rag to remove soil particles or dust
            from the area to be seamed.

      (c)    If two seaming crews can work simultaneously on the same seam,
            begin seaming at the mid-point of the geomembrane panels and work
            toward the ends. This tends to prevent fishmouths  occurring in
            the center of the panel.   On slopes,  seaming should proceed
            uphill.

                                      145

-------
 Rope for
advancing
 seaming
 board
v /
\/
RlLx;
ik rj1""""'""1"
L V{ ^
k *
k \\ 	
	 Upper Geomembrane 	
 of Lower Geomembrane

t> \ \ \ \ \ X "V \\\ \\ N
f50 mm (2 in.)
^Unbonded Overlap 	 1SO mm" (6 in-)
100 mm (4 in.) OverlaP Width
Seam Width
/// // // / / / / / / A

A^~1
,J
^ 1
250 mm
Seaming

-------
(d)   In constructing field seams one invariably encounters areas where
      three thicknesses of material need to be bonded together.  These
      areas occur at the intersection of factory and field seams and are
      known as "T" connections, see Figure 10.7 for schematic
      representation of the "T" connection.  Either additional adhesive
      should be used in these areas to bond the loose flap or the loose
      portion of the flap should be trimmed off, see Figure 10.8.

      For reinforced georaembranes one should discourage this type of
      trimming because it exposes the scrim reinforcement.  Such exposed
      scrim should be avoided since moisture and/or leachate could wick up
      the scrim and cause delamination or other undesirable effects.
      Reinforced geomembranes should be trimmed as accurately as possible
      with a razor hook knife,  with a backing to prevent damage to the
      underlying geomembrane.  In all locations where the ends of scrim
      are exposed one should use bodied adhesive chemicals or sealants
      which, due to their higher viscosity, can be more generously applied
      (called "flood coating")  in these regions.  All exposed scrim should
      be sealed.

(e)   Adhesive is applied uniformly to the bottom of the upper sheet and
      to the top of the lower sheet.  This is a critical part of the
      adhesive seaming process.  Care must be taken to make sure that
      enough adhesive is applied to wet and fuse both surfaces that are
      being seamed.  This adequate coverage can be seen visually since
      properly wetted seams look different from non-wetted areas.  Excess
      adhesive must be wiped up quickly and prevented from puddling, which
      could damage the geomembrane.

(f)   After applying the adhesive, a dwell  time is required for the
      adhesive to soften the surface of the geomembrane sheets.  Dwell
      times for various thicknesses of different geomembranes are from 2
      to 5 seconds.  Note that  high ambient temperatures, strong wind,  and
      low relative humidity all tend.to reduce the time necessary for the
      adhesive to soften the surface of the sheet.  Therefore, if these
      conditions exist, the "dwell time" will  be decreased.  The
      determination of dwell time emphasizes the importance of the
      preparation and testing of test strips which were described earlier.

(g)   Following the dwell  time, the two liner surfaces are mated together
      and pressure is applied to the upper surface.   The pressure is
      applied with a roller or  other suitable pressure device.  The
      process involves rolling  the seam both in a parallel  and
      perpendicular or 45 degree direction  so as to mate and fuse the two
      surfaces,  to remove air pockets,  and  to force any excess adhesive
      toward and out of the exposed overlap edge,  see Figure 10.9(a-b).
      The seaming technician should make a  sufficient number of passes
      with the roller to insure that both surface mating and excess
      adhesive removal  have been accomplished.   Generally between 5-10
      passes in each direction  over a 60 cm (2 ft.)  length will  be needed.
      However,  the use of any alternative adhesive or pressure applicator


                                 147

-------
                   Factory Seams^ (previously made) 

                                           /
                                                          Field Seam
                                                          (to be made)
                              Field Seam "V-Ower Edge
                                          of Panel
     Figure  10.7.   Perspective diagram of  locations where
                    "T" configurations commonly occur.
Figure 10.8.   Photograph of "T" trimming tool  shaving the upper
               surface  of an existing seam  in preparation of new
               intersecting seam.
                               148

-------
                         Upper Geomembrane 
                                                      Edge of Lower
                                                       Geomembrane
N
X
\
\
s.
N cn X . X XXXXXXXNX NW
IJ 50 mm (2 in.)
lynraonoBni tana ^.^ m (start)

Y ILTzona'"0 ( * ^ 5 passes
V / sv/ / s / /^ / / / / /' ' s )/ / A
(finish) j 1^
I Approximately 60 cm (2 ft.) Q<
^-  Lower Geomembrane 	 ^
100 mm (4 in.)
Overlap Zone
I/
ge of Upper
somembrane
  Figure 10.9(a).   Initial  rolling motion parallel  to seam for the
                   fabrication of adhesive seams for CPE,  CSPE,  EIA
                   or PVC liners.

      must be evaluated on  the test strip seams. The area that is
      rolled or pressed must be continuous.

(h)    Rolling should be accomplished at a somewhat  tacky stage using
      uniform pressure in a flowing motion,  see Figure 10.9(b).   This
      will lead to an acceptable seam with no entrapped vapor or air
      pockets.   Excessive pressure is not required.
                          Upper Geomembrane 

^ \
f Edge of Lower
/ Geomembrane
^ SO mm (2 in.)
lnhonrinriV7flna,.^f..rt.gTj^- _. -^. ^ -
\ * i, * ,
/50mm (2 in.) I .. 1 .
. SeamlZone t r T. '
///*//s^J/.)/ L> .^
Approximately 60 cm (2 f
1 8 passes
^-  Lower Geomembrane 	 ^
art)
100 mm (4 in.)
Overlap Zone
'/
\ Edge of Upper
Geomembrane
 Figure 10.9(b).   Final  rolling motion perpendicular to seam for the
                  fabrication of adhesive seams for CPE,  CSPE,  EIA or
                  PVC liners.
                                 149

-------
I
     (i)    After rolling a section of seam,  any excess  adhesive should be wiped
           off the top of the geomembrane.   Wipe toward the leading edge of the
           seam not away from it.   For reinforced geomembranes it is desirable
           to see a small bead of  adhesive  at the outer edge of the seam.

     (j)    With this seaming method the adhesive remains in the bonded area and
           becomes a component of  the seam.

     (k)    Clean pressure applicators should be used at all times.   When a
           roller is used, a clean surface  must be maintained.


10.5  AFTER SEAMING

     (a)    The seam must be checked visually for uniformity of width and surface
           continuity.  As stated  earlier,  proper adhesive application visually
           changes the surface appearance.   Usually the installer will use an
           air lance or blunt-end  pick, see Figure lO.lO(a-b), to check for
           voids or gaps under the overlapping geomembrane.

     (b)    When unbonded areas are located,  they can sometimes be repaired by
           inserting more adhesive into the opening and rolling.  If that is not
           satisfactory, a patch must be placed over them with at least 15 cm
           (6 inches) of geomembrane extending on all sides.

     (c)    Any area of the geomembrane sheets where adhesive accidentally
           spilled and caused damage greater than 10% of the original thickness,
           must be patched as above with at least 15 cm (6 inches)  of
           geomembrane extending beyond the affected areas.

     (d)    Any area of the geomembrane sheets where puncture holes are observed
           must be patched as above with at least 15 cm (6 inches)  of
           geomembrane extending beyond the affected areas.

     (e)    Note that with the above three repair items (b, c, and d) it is not
           practical to use a seaming board beneath the geomembrane.  However,
           a piece of the liner material can be used for added support under
           the liner, if needed, even if the hole must be enlarged to insert the
           piece before the patch  is made.   This added piece is left there
           indefinitely.  In either situation, additional care is necessary to
           insure a proper bond.

     (f)    Sandbags used to resist wind uplift stresses may to be placed on the
           seamed areas  in accordance with customary installation practice or as
           prescribed in the contract specifications.

     (g)    Cross sections of the completed seams are shown in Figure lO.ll(a-c).
                                             150

-------
         (a)  Air lance test.
(b)  Pick test.
Figure 10.10.   Photographs of air lance  and  pick  testing of completed  seam.
                                    151

-------
              Figure  10.11(a).
  Cross sections of CSPE-R seams fabricated by the
  chemical adhesive seaming method showing left
  side of completed seam.
I
           Figure  10.11(b).
Cross sections of CSPE-R seams fabricated by the
chemical adhesive seaming method showing center
side of completed seam.
                                            152

-------
Figure 10.11(c).
Cross sections of CSPE-R seams fabricated by the
chemical adhesive seaming method showing right
side of completed seam.
10.6  UNUSUAL CONDITIONS

     This section is written to give insight into conditions which go beyond
the general description just presented.

     (a)   High winds, or gusts of wind,  are always problematic for liners.
           After deploying the geomembrane,  the panels should be adequately
           ballasted, e.g., with sandbags.  The actual seaming operation,
           however,  may require the removal  of some of the ballast leaving the
           windward edge vulnerable to wind  uplift forces.  If possible,  proper
           orientation of the overlap might  be helpful.   Otherwise, additional
           labor may be required to only  remove sandbags immediately in front
           of the seaming operation.  The liner must be  cleaned of any dirt and
           moisture left behind after sandbag removal.  They are then to  be
           replaced behind the completed  seaming operation.
                                      153

-------
            (b)    Patches  are  invariably necessary to make at  locations where
                  destructive  test  samples are removed or where  seams  are  shown  to
                  fail  nondestructive testing.  These patches  must extend  a minimum  of
                  15  cm (6 inches)  beyond the outer  limits of  the area to  be repaired.
                  Since a  seaming board cannot be used in these  areas, additional care
                  is  necessary.  Sometimes excess pieces of geomembrane material which
                  are left in  place, are positioned  beneath the  area to be seamed.

            (c)    Details  around sumps, pipes and other appurtenances  are  perhaps the
                  most  demanding locations in an entire facility to properly seam.
                  Also  due to  their typical  locations being at low points  of the
                  containment  facility's design, these areas inherently operate  under
                  larger hydraulic  heads.  Should a  defect from  improper seaming occur
                  in  such  a location leakage rates and its associated  adverse  impacts
                  are heightened.   Therefore, extreme care should be exercised in
                  ensuring seam  integrity in these often difficult to  reach locations.
                  The adhesive should be placed symmetrically  on both  liners to  be
                  joined which may  be difficult for  external and internal  edges  and
                  particularly at corners.   Hand and finger pressure is needed in
                  tight locations.

            (d)    This  section was  written for material temperatures that  range
                  between  0C  (32'F) and 50C (122'F).  This is  the temperature  range
                  that  is  generally recognized as being acceptable for seaming without
                  taking special precautions.

                  For sheet temperatures below 0C (32F), shielding,  preheating,
                  different chemical compounds and/or a slower seaming rate may  be
                  required. More frequent seam testing and precautions to prevent
                  thawing  subgrade  (previously discussed) may  have to  be taken.
                  Sharp, frozen  subgrade should be avoided or  perhaps  a geotextile
                  used  to  eliminate point pressure damage potential.

                  For sheet temperatures above 50C  (122'F), shielding and rate  of
                  seaming  should be adjusted.  More  frequent destructive seam  testing
                  may have to  be taken.
I
                                             154

-------
FIELD NOTES:
                                      155

-------
      FIELD NOTES:
I
                                             156

-------
                                   SECTION 11

                 EMERGING TECHNOLOGIES FOR GEOMEMBRANE SEAMING


     Selected geomembrane sheet seaming methods which are not widely used at
the present time are discussed in this section.  These include ultrasonic
seams, electrical conduction bonding and magnetic induction bonding methods.

     The physical principles of each of these techniques are discussed, as
well as their current degree of development and implementation.  The potential
advantages and disadvantages of the methods are also discussed.


11.1  ULTRASONIC SEAMS

     Ultrasonic methods are used by various industries in a variety of ways.
These include product cleaning, thickness gauging, nondestructive flaw
detection, hardness testing, exotic machining, emulsification, sewing,
biological cell disruption, bonding of quite dissimilar materials (as in the
microelectronics area) and, of course, joining plastics.  The technique is
well advanced and fully implemented in areas other than geomembrane seaming.

     In ultrasonic seaming of thermoplastics,  an intense local vibration is
induced at the material interface by means of a piezoelectric, or
magnetostrictive, driven horn, see Figure 11.1.  The exact mechanism of the
bonding is not completely understood but it involves friction-driven melting
(at least locally) of the plastic and subsequent solidification and bonding.
Pressure is usually applied to the interface during the bond's formation.   It
is also suggested that the breaking of non-resin materials (e.g,  oxides) at
the interface may be inherent to the bonding process.  The frequencies of
vibration in ultrasonic welding are usually in the tens of kilohertz range.
The weld time is typically very short; on the  order of a few seconds.

     Figure 11.2 is a schematic drawing of the ultrasonic seaming process  for
seaming of geomembrane sheets.  The sheet material to be seamed is fed between
the two rollers; between the sheets is located the ultrasonic horn.   The horn
vibrates longitudinally at approximately 40,000 Hz (cycles/sec) and works  in
the squeeze roller nip areas directly against  the two surfaces to be joined.
The vibrational peak-to-peak amplitude is about 0.038 mm (0.0015  in.).  The
vibrating action works with the frictional characteristics of the material  to
produce the heat for melting and bonding the geomembrane.  Materials with
higher frictional coefficients produce heat more rapidly.  Knurled surfaces
are usually incorporated into the working areas of the horn to better engage
the material,  to disrupt any surface contaminants, to concentrate the energy
and to provide for mixing of the molten polymer just as the sheets are
entering the squeeze portions of the rollers.   The unit can seam  thermoplastic


                                      157

-------
     Plastic Sheets
                    Horn
      Anvil

^^vj
                                 Metal Sheets
Lr"
                (a)
                                            Ib)
 Figure 11.1.  Schematic diagrams of ultrasonic welding of
              plastic (and metal) sheets.
Figure  11.2.  Schematic diagram of rollers,  ultrasonic horn
             and geomembrane sheets in the  ultrasonic seaming
             process.  The method is called the  "Ultrascanner"
             by the developers.
                          158

-------
to 1.5 meters/min. (3-5 feet/minute).  Shear and peel values of the completed
seams are reported to be as good as with traditional seaming techniques.


11.2  ELECTRICAL CONDUCTION SEAMING

     In the electrical conduction seaming technique for plastics, electric
current is passed through wires embedded in (or placed between) the vicinity
of the parts to be joined.  The temperature of the wires rises via ohmic
heating and the heat is transferred to the plastic which melts in the vicinity
of the wires.  Upon solidifying, the parts are joined.  Pressure is usually
applied, either physically, or indirectly by differences in thermal expansion
of the parts.  Both ac and dc currents have been used.  Welding times are
typically the same as those common in the geomembrane heat fusion techniques,
for it is essentially a thermal technique.  This particular seaming method is
widely used in the natural gas plastic pipeline area and is usually called the
"electro-fusion" technique.  Figure 11.3 gives a schematic diagram of the
electro-fusion process which indicates that certain properties are measured in
real-welding time, and fed back to the control panel to readjust and optimize
welding conditions.

     Initial tests on this type of seaming of geomembranes were on a 1.5 mm
(60 mils) HOPE geomembrane.  Stainless steel wires were braided around a 0.6
cm (1/4 inch) diameter HOPE core.  Figure 11.4 shows a sketch of the assembly.
A force was applied normal to the sheets with the braided wire between.
Electrical current (ac) of 5-10 amperes was passed through the wires.  The
wires heat due to ohmic effects and melt the core and the adjacent sheet
material.  The current was stopped after a prescribed time and the material
subsequently solidified, thereby bonding the sheets together.  Under the
present experimental  circumstances, maximum weld lengths of about 1 meter
(3 feet) can be made with a single application of the current electrodes.

     To date the electrical conduction technique has not been used to field
seam geomembranes and is currently in an experimental stage.


11.3  MAGNETIC INDUCTION SEAMING

     In electromagnetic induction seaming, a conductor and/or hysteretic
material (in the form of wires, particles, strips,  etc.) is placed at the
interface to be joined.  A non-contacting, induction coil  containing high
frequency electric current passes over the area to be seamed.  The
time-varying magnetic field caused by the current in the coil induces eddy
currents and/or hysteresis loss in the embedded materials.   Hence the area is
heated,  melts,  solidifies and bonding takes place.   Pressure is usually
applied to the interface.  Frequencies generally range from 3-7 MHz and 80-320
KHz,  depending on the particular application.   A wide variety of plastic
assembly and sealing  applications have been performed.   The electromagnetic
induction method has  been mentioned briefly in the natural  gas pipeline
literature,  but no details are available as to its use.
                                     159

-------
         Figure 11.3.  Schematic diagram of an  electrofusion pipe coupling process.
I
                  CORE
                                             VOLTAGE
                                            0SOURCE
CURRENT
               Figure 11.4.  Schematic diagram of  the electrical conduction
                             method of joining geomembranes.
                                           160

-------
     Figure 11.5 is a schematic diagram of the fabrication  process  of
electromagnetic induction seaming for geomembranes.   An  HOPE  sheet  of  0.945
g/cm3 density and 1.5 mm (60 mils) thickness  was  used in the  tests.  The
braided core, made by the same process as described  for  the electrical
conduction method is placed between the two sheets and force  is  applied normal
to the sheet.  An electromagnetic coil carrying high frequency alternating
current of about 200 KHz is passed directly over  the braided  core.   No contact
whatsoever is made between the electromagnetic coil  and  the sheet.   The coil
is about 0.6 cm (1/4 inch) to 1.2 cm (1/2 inch) above the top geomembrane
sheet.  Eddy currents are induced in the embedded braided wire by the
time-varying magnetic field.  This results in ohmic  heating which melts the
core and a certain amount of the adjacent sheet material.   After the coil has
passed, the eddy currents cease and the material  solidifies and  bonds  the
sheets together.  Rates of about 0.3 m/min.  (1.0  ft/min.) have been  achieved.
Preliminary results of mechanical testing of  the  seams give about 90%  of sheet
value for shear but are very poor in peel.  By optimization of the  welding
parameters, this situation may improve.

     To date the magnetic induction technique has not been  used  to  field seam
geomembranes and is currently in an experimental  stage.
                                                  HIGH  FREQUENCY
                                                  ALTERNATING  CURRENT
    CORE
                 PRESSURE
       Figure 11.5.   Schematic  diagram  of  the magnetic induction method
                     of joining geomembranes.

                                     161

-------
FIELD NOTES:
                                      162

-------
                                   SECTION 12

                                   REFERENCES


1.   Frobel, R. K.,  "Methods of Constructing and Evaluating Geomembrane
            Seams,"  Proc. Conf. on Geomembranes, Denver, CO., 1984,
            IFAI, pp. 359-364.

2.   Lord, A. E. Jr., Koerner, R. M. and Crawford, R. B., "Nondestructive
            Testing  Techniques to Assess Geomembrane Seam Quality," Proc.
            Mgmt. of Uncontrolled Haz. Waste Sites, Washington, DC, 1986,
            HMCRI, pp.  272-276.

3.   Overmann, L. K., "Nondestructive Seam Testing: CQC Perspectives,"
            Proc. on the Seaming of Geosynthetics, Journal of Geotextiles
            and Geomembranes, Elsevier Appl. Sci. Pub. Ltd., Vol., No. 4-6,
            1990, pp. 415-430.

4.   Richardson, G.  N., "Nondestructive Seam Testing: CQA Perspectives,"
            Proc. on the Seaming of Geosynthetics, Journal of Geotextiles
            and Geomembrane, Elsevier Appl. Sci. Pub. Ltd., Vol. 9, No. 4-6,
            1990, pp. 445-450.

5.   Haxo, Henry E.  Jr., and L. C. Kamp, "Destructive Testing of Geomembrane
            Seams: Shear and Peel Testing of Seam Strength," Proc. on the
            Seaming  of Geosynthetics, Journal of Geotextiles and Geomembranes,
            Elsevier Appl. Sci. Pub. Ltd., Vol. 9, No. 4-6, 1990, pp. 369-396.

6.   Peggs, Ian D.,  "Destructive Testing of Polyethylene Geomembrane Seams:
            Various Methods to Evaluate Seam Strength," Proc. on the Seaming
            of Geosynthetics, Journal of Geotextiles and Geomembranes, Elsevier
            Appl. Sci. Pub. Ltd., Vol. 9, No. 4-6, 1990, pp. 405-414.

7.   Matrecon, Inc., "Lining of Waste Containment and Other Impoundment
            Facilities," EPA/600/2-88/052, NTIS PB89-129670, Sept. 1988.

8.   U.S. EPA Technical  Guidance Document, "Construction Quality Assurance
            for Hazardous Waste Land Disposal Facilities," EPA/530-SW-86-031,
            NTIS PB87-132825, Oct. 1986.

9.   Haxo, H.  E. Jr., "Quality Assurance of Geomembranes Used as Linings for
            Hazardous Waste Containment," Journal  of Geotextiles and
            Geomembranes,  Vol. 3, No. 4, 1986,  pp. 225-248.
                                      163

-------
       10.  Apse, J.  I.,  "Polyethylene Resins for Geomembrane Applications,"
                   Proc.  on Aging and Durability of Geosynthetics, R. M. Koerner,
                   Ed., Elsevier Appl. Sci. Pub. Ltd., 1989, pp.  159-176.

       11.  ASTM, Proposed Document for Task Committee D-4000 on  Plastic Liners,
                   June,  1989.

       12.  Koerner,  R. M., Designing with Geosynthetics, 2nd Edition, Prentice
                   Hall Publ. Co., Englewood Cliffs, NO, 1990.

       13.  Koerner,  G. R. and Bove, J. A., "Construction Quality Assurance of
                   HOPE Geomembrane Installations," Proc. Geosynthetics  '89,
                   San Diego, CA., IFAI, pp. 70-83.

       14.  ASTM D 4439,  "Terminology for Geosynthetics," American Society for
                   Testing and Materials, Philadelphia, PA.
I
                                              164

-------
FIELD NOTES:
                                     165

-------
FIELD NOTES:
                                      166

-------
                                  SECTION 13

                               GLOSSARY OF TERMS


Air Lance - A commonly used nondestructive test method performed with a stream
     of air forced through a nozzle at the end of a hollow metal tube to
     determine seam continuity and tightness of relatively thin, flexible
     geomembranes.

Adhesive - A chemical system used in the bonding of geomembranes.  The
     adhesive residue results in an additional element in the seamed area.
     (Manufacturers and installers should be consulted for the various types
     of adhesives used with specific geomembranes.)

Anvil - In hot wedge seaming of geomembranes, the anvil is the wedge of metal
     above and below which the sheets to be joined must pass.  The temperature
     controllers and thermocouples of most hot wedge devices are located
     within the anvil.

Bodied Chemical Fusion Agent -  A chemical fluid containing a portion of the
     parent geomembrane that, after the application of pressure and after the
     passage of a certain amount of time, results in the chemical fusion of
     two essentially similar geomembrane sheets, leaving behind only that
     portion of the parent material.  (Manufacturers and installers should be
     consulted for the various types of chemical fluids used with specific
     geomembranes in order to inform workers and inspectors.)

Buffing - An inaccurate term often used to describe the grinding of
     polyethylene geomembranes to remove surface oxides and waxes in
     preparation of extrusion seaming.

Chemical-Adhesive Fusion Agent - A chemical  fluid that may or may not contain
     a portion of the parent geomembrane and an adhesive that, after the
     application of pressure and after passage of a certain amount of time,
     results in the chemical fusion of two geomembrane sheets, leaving behind
     an adhesive layer that is dissimilar from the parent liner material.
     (Manufacturers and installers should be consulted for the various types
     of chemical fluids used with specific geomembrane to inform workers and
     inspectors.)

Chemical Fusion - The chemically-induced reorganization in the polymeric
     structure of the surface of a polymer geomembrane that, after the
     application of pressure and the passage of a certain amount of time,
     results in the chemical fusion of two essentially similar geomembrane
     sheets being permanently joined together.


                                      167

-------
Chemical Fusion Agent - A chemical fluid that, after the application of the
     passage of a certain amount of time, results in the chemical fusion of
     two essentially similar geomembrane sheets without any other polymeric or
     adhesive additives.  (Manufacturers and installers should be consulted
     for the various types of chemical fusion agents used with specific
     geomembranes to inform workers and inspectors.)

Chlorinated Polyethylene (CPE) - Family of polymers produced by the
     chemical reaction of chlorine with polyethylene. The resultant polymers
     presently contain 25-45% chlorine by weight and 0-25% crystallinity.

Chlorinated Polyethylene-Reinforced (CPE-R) -Sheets of CPE with an
     encapsulated fabric reinforcement layer, called a "scrim".

Chlorosulfonated Polyethylene (CSPE) - Family of polymers produced by the
     reaction of polyethylene with chlorine and sulphur dioxide.  Present
     polymers contain 23.5 to 43% chlorine and 1.0 to 1.4% sulphur.  A "low
     water absorption" grade is identified as significantly different from
     standard grades.

Chlorosulfonated Polyethylene-Reinforced (CSPE-R) - Sheets of CSPE with an
     encapsulated fabric reinforcement layer, called a "scrim".

Construction Quality Assurance (CQA) - A planned system of activities
     whose purpose is to provide an evaluation of the completed liner
     and initiate corrective action where necessary.

Construction Quality Control (CQC) - Actions that provide a means of
     monitoring and measuring the quality of the product as it is being
     installed.

Crystal Structure - The geometrical arrangement of the molecules that occupy
     the space lattice of the crystalline portion of a polymer.

Curing - The strength gain over time of a chemically fused, bodied chemically
     fused, or chemical adhesive geomembrane seam due primarily to evaporation
     of solvents or crosslinking of the organic phase of the mixture.

Curing Time - The time required for full curing as indicated by no further
     increase in strength over time.

Destructive Tests - Tests performed on geomembrane samples cut out of a field
     installation or test strip to verify specification performance
     requirements, e.g., shear and peel tests of geomembrane seams during
     which the specimens are destroyed.

Drive Rollers - Knurled or rubber rollers which grip the geomembrane sheets
     via applied pressure and propel the seaming device at a controlled rate
     of travel.
                                      168

-------
Dwell Time - The time required for a chemical fusion, bodied chemical fusion
     or adhesive seam to take its initial "tack", enabling the two opposing
     geomembranes to be joined together.

Environmental Stress Crack  (ESC) - see also Stress Crack - External or
     internal stress propagation in a plastic caused by environmental
     conditions which are usually chemical or thermal in nature.

Ethylene Interpolymer Alloy (EIA)- A blend of ethylene vinyl acetate and
     polyvinyl chloride resulting in a thermoplastic elastomer.

Ethylene Interpolymer Alloy-Reinforced (EIA-R) - Sheets of EIA with an
     encapsulated fabric reinforcement layer.

Extrudate - The molten polymer which is emitted from an extruder during
     seaming using either extrusion fillet or extrusion flat methods.  The
     polymer is initially in the form of a ribbon, rod, bead or pellets.

Extrusion Seams - A seam between two geomembrane sheets achieved by heat-
     extruding a polymer material between or over the overlap areas followed
     by the application of  pressure.

Factory Seams - The seaming of geomembrane rolls together in a factory to make
     large panels to reduce the number of field seams.

Field Seams - The seaming of geomembrane rolls or panels together in the field
     making a continuous liner system.

Fishmouth - The uneven mating of two geomembranes to be joined wherein the
     upper sheet has excessive length that prevents it from being bonded flat
     to the lower sheet.  The resultant opening is often referred to as a
     "fishmouth".

Flashing - The molten extrudate or sheet material which is extruded beyond
     the die edge or molten edge, also called "squeeze-out".

Flexible Member Liner (FML) - Synonymous term for geomembrane.

Flood Coating - The generous application of a bodied chemical compound,  or
     chemical adhesive compound to protect exposed yarns in scrim reinforced
     geomembranes.

Geomembrane - An essentially impermeable membrane used as a solid or liquid
     barrier.  Synonymous term for flexible membrane liner (FML).

Geotextile - Any permeable textile used with foundation,  soil,  rock,
     earth,  or any other geotechnical  engineering-related material  as an
     integral part of a human-made project,  structure, or system.

Grinding - The removal  of oxide layers and waxes from the surface of a
     polyethylene sheet in preparation of extrusion fillet or extrusion  flat
     seaming.

                                      169

-------
Gun - Synonymous term for hand held extrusion fillet device or hand held
     hot air device.

High Density Polyethylene (HOPE) -  A polymer prepared by low-pressure
     polymerization of ethylene as the principal monomer and having the
     characteristics of ASTM D1348 Type III and IV polyethylene.  Such
     polymer resins have density greater than or equal to 0.941 g/cc
     as noted in ASTM D1248.

Hook Blade - A shielded knife blade confined in such a way that the blade
     cuts upward or is drawn toward the person doing the cutting to avoid
     damage to underlying sheets.

Horn - The vibrating device used with ultrasonic seaming which vibrates at
     high frequency causing friction and a subsequent melting of the surfaces
     that it contacts.

Initial Reaction Time - Dwell time.

Medium Density Polyethylene (HOPE) - A polymer prepared by low-pressure
     polymerization of ethylene as the principal monomer and having the
     characteristics of ASTM D1348 Type II polyethylene.  Such polymer resins
     have density less than 0.941 g/cc as noted in ASTM D1248.

Mouse - Synonymous term for hot wedge, or hot shoe, seaming device.

Nondestructive Test - A test method which does not require the removal of
     samples from, nor damage to, the installed liner system.  The evaluation
     is done in an in-situ manner.  The results do not indicate the seam's
     mechanical strength.

Oxide Layer - The reacting of atmospheric oxygen with the surface of the
     polymer sheet.

Pinholes - Very small imperfections in sheet or seamed geomembranes which may
     allow for escape of the contained liquid.

Plasticizer - A material, generally an organic liquid, incorporated in a
     plastic or rubber formulation to soften the resin polymer and improve
     flexibility, ductility and extensibility.

Polyethylene (PE) - A semi crystalline thermoplastic'polymer made by
     polymerizing ethylene and other co-monomer(s).

Polymer - A carbon based organic chemical material formed by the chemical
     reaction of monomers having either the same or different chemical
     structures.  Plastics, rubbers and textile fibers are all relatively high
     molecular weight polymers.
                                      170

-------
Polyvlnyl Chloride  (PVC) - A non-crystalline thermoplastic polymer composition
     prepared from  polymerized vinyl monomer by blending with one or more low
     or non-volatile plastisizers made by polymerizing vinyl chlorine monomer.

Pressure Rollers -  Rollers accompanying a seaming technique which apply
     pressure to the opposing geomembrane sheets to be joined.  They closely
     follow the actual melting process and are self-contained within the
     seaming device.

Puckering - A heat  related sign of localized strain caused by improper
     seaming using  extrusion or fusion methods.  It often occurs on the bottom
     of the lower geomembrane and in the shape of a shallow inverted "V".

Quality Assurance - See construction quality assurance.

Quality Control - See construction quality control.

Scrim Designation - The weight and number of yarns of fabric reinforcement
     per inch of length and width, e.g, a 10 X 10 scrim has 10 yarns per inch
     in both the machine and cross machine directions.

Scrim (or Fabric) Reinforcement - The fabric reinforcement layer used with
     some geomembranes for the purpose of increased strength and dimensional
     stability.

Sealant - A viscous chemical used to seal the exposed edges of scrim
     reinforced geomembranes. (Manufacturers and installers should be
     consulted for  the various types of sealant used with specific
     geomembranes).

Seaming Boards - Smooth wooden planks placed beneath the area to be seamed
     to provide a uniform resistance to applied roller pressure in the
     fabrication of seams.

Shielded Blade - A  knife within a housing which protects the blade from
     being used in an open fashion, i.e., a protected knife.

Squeeze-Out -See "flashing".

Solvent, Bodied Solvent and Solvent Adhesive - See Chemical Fusion, Bodied
     Chemical  Fusion and Chemical Adhesive.

Stress Crack - ASTH D1693 - An external or internal rupture in a plastic
     caused by tensile stress less than its  short-time mechanical  strength.

Stress Crack - ASTN D883 - An external  or internal  crack in a plastic caused
     by tensile stresses less than its  short-time mechanical strength.
     Note:   The development of such cracks is frequently accelerated by the
     environmental  to which the plastic is exposed.  The stresses  which cause
     cracking  may be present internally or externally or may be combinations
     of these  stresses.
                                      171

-------
Tack - Stickiness.

Tensiometer - A device containing a set of opposing grips used to place a
     geomembrane seam in tension for evaluating its strength in shear or in
     peel.

Test Strips - Trial sections of seamed geomembranes used (1) to establish
     machine setting of temperature, pressure and travel rate for a specific
     geomembrane under a specific set of atmospheric conditions for machine-
     assisted seaming and (2) to establish methods and materials for chemical
     and chemical adhesive seams under a specific set of atmospheric
     conditions.

Test Welds - See "test strips".

Thermal Fusion - The temporary, thermally-induced reorganization in the
     polymeric make-up of the surface of a polymer geomembrane that, after the
     application of pressure and the passage of a certain amount of time,
     results in the two geomembranes being permanently joined together.

Thermoplastic Polymer - A polymer that can be heated to a softening point,
     shaped by pressure, and cooled to retain that shape.  The process can be
     done repeatedly.

Thermoset Polymer - A polymer that can be heated to a softening point,
     shaped by pressure, and, if desired, removed from the hot mold without
     cooling.  The process cannot be repeated since the polymer can not be
     resoftened by the application of heat.

Vacuum Box - A commonly used type of nondestructive test method which
     develops a vacuum in a localized region of an geomembrane seam in order
     to evaluate the seam's tightness and suitability.

Very Low Density Polyethylene (VLDPE) - A linear polymer of ethylene with
     other alpha-olefins with a density of 0.900 to 0.910.

Waxes - The low molecular weight components  of some polyethylene compounds
     which migrate to the surface over time  and must be removed by grinding
     (for HOPE) or be mixed into the melt zone using thermal seaming methods.

Wicking - The phenomenon of liquid transmission within the fabric yarns of
     reinforced geomembranes via capillary action.
                                      172

-------
FIELD NOTES:
                                     173

-------
FIELD NOTES:
                                      174
                       6 U.S. GOVERNMENT PRINTING OFFICE: 1991 548-187/25637

-------