United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/038 July 1987
Project Summary
Assessment of Techniques for
In Situ Repair of Flexible
Membrane Liners: Final Report
H. E. Haxo, Jr.
The feasibility of using either patch-
ing or plugging to make in situ repairs
of damaged areas in in-service flexible
membrane liners (FMLs) was investi-
gated. Applying the basic criteria used
in assessing and testing liners and
seams in FMLs that are being installed,
it appears highly questionable that
conditions required for preparation of
adequate seams and permanent repairs
can be met with FMLs exposed below
wastes. Exposed liners, however, can
be repaired if the proper conditions of
cleanliness and dryness are met.
Repairing with formed-in-place plugs
holds some promise for short-term use;
however, the compatibility of the
plugging material with the waste liquid
should be assessed.
Experimental studies relating to
preparation of high density polyethy-
lene (HOPE) seams made with a heat
gun indicate the importance of surface
preparation in achieving adhesion
between the two pieces of liner being
seamed. Cleanliness and fresh surfaces
are necessary. Compatibility tests of six
different potential plugging materials
(five epoxies and one cement) in five
simulated test media show the impor-
tance of the medium on the ability of
the material to set and with long-term
integrity of the cured materials.
This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research Laboratory, Cincin-
nati, OH, to announce key findings of
the research project that is fully doc-
umented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The use of flexible membrane liners
in liner systems for waste storage and
disposal facilities has been increasing
over the past decade. The principal basis
for this application of FMLs is their low
permeability to liquid flow and their
ability to minimize the escape of waste
constituents and subsequent contamina-
tion of surface or groundwater. While
these liners can be quite effective in
reducing environmental contamination,
the potentially low permeability of the
liner can be compromised by membrane
defects during manufacture, by seam
defects, by excessive swelling, or by
damage occurring accidentally during
installation or as a result of wear and
tear during service.
In view of the desirability of being able
to repair damaged in-place FMLs without
having to remove large quantities of
waste from above them, the original
project was undertaken to assess the
feasibility of making permanent in situ
repairs of in-place membrane and admix
liner systems.
The full report of this study discusses
the technical requirements and condi-
tions for in situ repairs of FMLs at various
times during installation and service. The
results of searching the existing techni-
cal literature on seaming polymeric
sheeting and the results of discussing the
general industry practice with technical
experts are presented, along with labor-
atory results using different repair
techniques. Laboratory test procedures
used in assessing repair methods are
described and test results are presented.
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Summary of Work
The open technical literature was
searched for information on the repair
of FMLs. The search included literature
on adhesion, adhesives, and various
methods of seaming coated fabrics,
membranes, and FMLs. However, out-
side of work either performed by
Matrecon under previous EPA contracts
or observed by Matrecon personnel, little
information was found relating to the
repair of FMLs in the field or under
simulated field conditions.
The general concept of repairing liners
was investigated with particular refer-
ence to potential problems that might
occur during the different phases in the
life of a liner. Also investigated was the
concept of temporary versus permanent
repair.
Criteria for repairing liners in the field
were scrutinized. It was felt that the basic
requirement for a permanent repair
should be that it meet the same criteria
that the liner and seam must meet at
the time of liner installation. If a patch
is used, its adhesion to the liner should
equal that of the original seams. On the
other hand, if a formed-in-place plug is
used to repair a hole in a liner, chemical
adhesion to the liner may not be required
if a sufficiently high mechanical bond is
formed between the liner and the plug.
The consensus of a panel of experts
in this field was that work should be
concentrated on investigating the repair
of damage to HOPE FMLs and possibly
the use of plugs for repairing damage to
FMLs below ground level. The following
tasks were recommended by the panel
and were undertaken:
1. Assess methods of seaming
polyethylene with a Leister gun and
by spin-welding.
2. Assess the compatibility of polyeth-
ylene seams in contact with a
series of five test media. These test
media included deionized water,
10% HCI, 10% NaOH, a 5% solution
of mineral oil in xylene, and a mixed
solvent containing equal volumes
of chloroform, methyl ethyl ketone,
and cyclohexane.
3. Assess the compatibility of six
potential plugging materials in
contact with the same series of five
test media. These potential plug-
ging materials were all hardenable
liquid compositions and included
five epoxies and one hydraulic
cement. In one study, the ability of
the plugging materials to harden in
the presence of the test media was
determined and, if they did harden,
whether they maintained their
properties in continued exposure.
A second study was performed in
which these plugging materials
were cured in air and then
immersed in the test media.
Conclusions
The long-term integrity of seams made
in a repair operation is questionable.
Repairing a damaged FML by patching
the liner with pieces of the same type
of membrane material of essentially the
same composition can only be performed
if the liner is clean and dry and has a
fresh surface. These conditions are
prerequisites for achieving good adhe-
sion between materials in general and
are very difficult to achieve in the
environment of waste disposal facilities,
except perhaps on slopes and in areas
of the FML not exposed to the weather
or to the waste.
The difficulties involved in making
quality repairs that meet the criteria
imposed on a newly installed liner make
it even more important to emphasize
quality control and quality assurance
during the construction of a disposal
facility and the installation of a liner so
as to minimize the possibility of liner
failure. It appears that, if there is
inaccessible damage below the waste in
an in-place liner, the damage is nonre-
pairable and it may be necessary to close
the disposal unit.
Plugging holes in a liner with harden-
able liquids, such as the epoxies, may
be feasible (1) if good mechanical bonds
can be made between the plug and the
liner, (2) if the liquid is deliverable to the
location of the damage, and (3) if the
plugging material is compatible with the
waste liquid during cure and subsequent
exposure. fc
Because of uncertainty about the
adequacy of liner repairs in situ below
solid waste levels, backup systems are
essential. Double liner systems may
provide that backup assurance necessary
to protect the groundwater system.
Recommendations
At the present state of liner technology
and given the difficulties involved with
repairing in-service FMLs and with
closing an impoundment unit once there
is damage to the liner, it is recommended
that large impoundment units be avoidei
and that smaller units be used which cat
be monitored individually. Small unit!
can be cleaned out or closed withou
moving massive quantities of waste, thus
reducing the risk of groundwate
contamination.
Information is lacking in the oper
technical literature on the durability o
FML seams, failures of in-service FMLs
and the repair of in-service FMLs. To fil
this need, field verification studies
should be undertaken to assess the types
of failures that occur. An effort shoulc
be made to locate and assess field repairs
of liners made during installation ano
performance testing.
Increased emphasis should be placed
on the development of seaming tech-
niques, including the development of
new techniques. Also, increased empha-
sis should be placed on seam testing to
ensure that seams with long-term integ-
rity and durability are prepared and
accepted during installation.
Samples of seams should be included
in the compatibility testing of the FMLs
during the liner selection and design
process. Quality assurance tests of
seams should be performed during liner
construction. In addition, seam samples
cut from the actual liner should be
exposed and routinely tested during
service to monitor any changes in seam
quality.
.S. GPO: 1987—748-012/67191
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Henry E. Haxo, Jr.. is with Matrecon, Inc., Alamada, CA 94501.
Robert P. Hartley is the EPA Project Officer (see below).
The complete report entitled "Assessment of Techniques for In Situ Repair
of Flexible Membrane Liners," (Order No. PB 87-191 813/AS; Cost: 313.95,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-87/038
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