United States
Environmental Protection
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-169 Jan. 1985
Project Summary
Liner Materials Exposed  to
Hazardous  and Toxic Wastes
H. E. Haxo, Jr., Robert S. Haxo, Nancy A. Nelson, Paul D. Haxo,
Richard M. White, and Suren Dakessian
  A research project was undertaken to
assess the relative effectiveness and
durability of a wide variety of liner ma-
terials when exposed  to  hazardous
wastes under conditions simulating
various aspects  of service in waste
storage and disposal facilities. The ma-
terials studied included compacted soil,
admixes, sprayed-on  asphalt, and 32
polymeric membranes.  Four partially
crystalline  polymeric  sheetings were
not compounded for use as liners but
were included in the study because of
their known' chemical resistance and
their use in applications requiring good
cheniical and aging resistance.
  flie lining materials were exposed in
test cells to 10 hazardous wastes (two
acidic, two alkaline, three oil, a blend
of lead, a pesticide, and an industrial.
waste) and three media of known com-
position—deionized water, 5%  aque-
ous solution of salt,  and a saturated
solution of low-concentration (0.1%)
organic tributyl phosphate. The,poly-
meric materials were also exposed to
wastes or environmental  conditions
under a variety of procedures that in-
cluded primary one-sided exposure, im-
mersion testing, two types of outdoor
exposure, and a pouch test. Some of
the exposures were as long*as 2700
days.   New   methods  for  testing
polymeric materials are presented.
  This Project  Summary was devel-
oped by EPA's Hazardous Waste  En-
gineering Research Laboratory, Cincin-
nati, OH, to announce key findings of
the research  project  that  is  fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
  Land disposal studies in the early
1970's clearly indicated the need for
positive  control measures to prevent
contamination of the surface water and
groundwater  that might result from
storage  and  disposal  of  hazardous
wastes on the land. The use of man-
made liner materials of low permeabil-
ity appeared to  be a feasible means of
preventing the pollutants in hazardous
wastes from entering the groundwater.
Some lining materials have been in use
for 20 years or more to impound water.
Liners have also been used to impound
brines and some wastes. A wide range
of materials differing in permeability,
composition,  construction,  and  cost
have been used or are potentially useful
for confining possible pollutants. Never-
theless, available data  on the relative
performance and service lives of  spe-
cific  materials  exposed  to   certain
wastes are meager. To guide and per-
haps eventually regulate the use of lin-
ers in these applications, the U.S. En-
vironmental  Protection  Agency (EPA)
needed considerably more information.
  This project was undertaken in  1975
with the following board objectives:

  1. To  determine  how  a selected
    group of lining materials is af-
    fected by exposure to a range of
    typical hazardous wastes  over a
    relatively  extended  period  (2
  2. To determine  the  durability and
    cost  effectiveness  of  polymeric
    membranes,  sprayed-on  mem-
    branes, admixed  materials,  and
    natural soils as liners for hazard-

     ous waste storage and  disposal
  3.  To estimate the effective lives of
     12 liner materials exposed to six
     types of nonradioactive hazardous
     waste streams under conditions
     that simulate those encountered in
     waste impoundment and disposal
  4.  To develop information needed for
     selecting specific lining materials
     to  confine hazardous wastes in
     specific installations.
  5.  To develop methods for assessing
     the relative merits of the various
     lining  materials for specific appli-
     cations and for determining their
     service lives.
  6.  To  develop  indicator tests  that
     could be used to  select lining ma-
     terials for given applications.
  7.  To help EPA develop effective con-
     trols for  the proper disposal and
     management     of    hazardous
  Results of this project have been re-
ported over the past  several  years in
various  preliminary  documents.  The
final report, summarized here, presents
the results of the complete project and
includes information on the exposure of
lining materials for periods of up to
2700 days (most of the exposure data
are for periods of up to 1350 days, how-

Materials and Methods

Types of Liners Used
  This  research program  determined
the effects of exposing a broad range of
selected liner materials to a  range of
wastes, sludges, and test media under
a variety of test conditions for periods
of up to 2700 days. The four types of
liner materials included in the program
  • One compacted soil of low permea-
  • Three  admixes (asphalt concrete,
    polymer-treated bentonite and sand
    mixtures, and a hydraulic cement)
  • One sprayed-on membrane of an
    emulsified asphalt on a nonwoven
  • Thirty-two  different  commercial
     polymeric sheetings based on the
    following polymer types:
      Butyl rubber
      Chlorinated polyethylene
      Chlorosulfonated polyethylene
      Elasticized polyolefin
      Polyester elastomer
      Polyethylene (low- and high-den-
      Polyvinyl chloride
  The  polymeric  materials covered a
range  of thicknesses,  manufacturers,
and crosslinked and thermoplastic vari-
ations of the same polymers, and some
were fabric-reinforced sheetings.
  Single  samples   of sheeting  of
polybutylene,  low-  and  high-density
polyethylene, and polypropylene were
included in the study because of their
promising characteristics  and use in
pipes and containers for handling cor-
rosive chemicals. None  of the sheetings
contained carbon black,  and none were
designed specifically for use as linings
for waste disposal facilities.

Wastes Tested
  The wastes studied represented sev-
eral general types, including two acidic
wastes  (one with a pH<1.0),  two al-
kaline wastes (one with a pH of >12.5),
one industrial waste (with high concen-
trations of trace  metals and organics,
one lead waste, three  oil wastes, and
one pesticide waste. In addition, three
test fluids of known composition were
included as reference points: Deionized
water,  5% solution  of  salt and water,
and saturated solution of tributyl phos-
phate (0.10%). The first two fluids could
be  used as  standard  references, as
many of the wastes that are encoun-
tered contain water and salt. The satu-
rated solution of tributyl phosphate was
included to assess the effect that occurs
when polymeric membranes absorb an
organic chemical  in  an aqueous solu-
tion of known low concentration.

Test Methods
Four major  types of  exposure  tests
were conducted on the lining materials:
    1. One-sided   exposure  to  the
      wastes. In  this  primary test of
      the  project,  liner   specimens
      about  0.092  m2 (1  ft2)  were
      mounted in cells (Figure 1), and
      a 0.030-m  (1-ft)  head of waste
      was placed on them. This test
      was designed to  simulate a liner
      at the bottom of a pond. The per-
      meability of the material could
      be assessed by collecting seep-
      age  below the  liner specimen.
      Durability  was   measured  in
      terms of property retention after
      two exposure periods. All four
  types of lining materials were in-
  eluded in this exposure test.
2. Two-sided  exposure   to   the
  wastes  by immersion.  Samples
  of 16 polymeric membrane  lin-
  ers were suspended in the tanks
  of the above cells containing 13
  waste liquids and test media. In
  most cases, two specimens of a
  membrane were placed in  the
  liquid, withdrawn at two differ-
  ent  times, and subjected to  a
  series of tests, including mea-
  surement of dimensions, weight
  increase,  volatiles content,  ex-
  tractables  content,  and  such
  physical tests as tensile, tear,
  and puncture resistance.
3. Outdoor exposure. Two types of
  outdoor  exposure were con-
  ducted.   The   first   exposed
  polymeric membrane  samples
  to weathering, and the second
  exposed samples intermittently
  to both weathering and a waste.
  In the first exposure, three speci-
  mens for each of the polymeric
  membranes were placed on  a
  roof rack in Oakland, California
  (Figure 2). One specimen was re-
  moved  after each of three time
  periods. The   specimens were
  measured   for    dimensional
  changes and  then tested  in  a
  manner similar to those in  the
  immersion test.  In the second
  type of outdoor exposure, poly-
  meric  membrane  liner speci-
  mens were used to line small
  tubs that contained wastes  (Fi-
  gure 3). This  test allowed  as-
  sessment of weather and waste
  exposure  on   the liner  below,
  above, and at the interface of the
  waste and air, and it tested the
  effect of directional orientation.
  The liner specimens in the tubs
  contained a field seam so  that
  the  effects of waste  on seam
  strength could also be assessed.
4. Pouch  test. Pouches fabricated
  from   polymeric  membranes
  were filled with wastes and sea-
   led   (Figure   4). The  sealed
   pouches   were  immersed  in
   deionized water and exposed for
   extended periods. The permea-
   bility of the membranes could
   be  assessed  by measuring at
   various time intervals the weight
   change of the pouch  and  the
   conductivity and pH changes of
   the deionized water in which the

                                              Top Cover
                                                         Steel Tank
                                                        Outlet Tube with
                                                   Top Cover
                      Epoxy Grout Ring

                                Admix Liner
                                                       Waste Column:
                                                    •—10"x15"x12" High
                                                           Outlet Tube with
Flanged Steel
                                                         Glass Cloth


Figure 1.    Design of cells for long-term exposure of membrane liners flop) and soil and admix
            liners (bottom) to various hazardous wastes.
       pouches were placed. When the
       pouches were  eventually  dis-
       mantled, dissected, and tested,
       they also yielded information on
       one-sided exposure to waste.

  The duration of these tests ranged up
to 2700 days for the primary tests, 1456
days for the immersion test, 1231 days
for the  roof rack test, and more than
2500 days for some  of the tubs. Some
of the pouch tests ran  as long as 2000
  In addition to the exposure studies, a
Variety of special tests were developed
for the polymeric membranes. These in-
cluded analyses for  ash, volatiles, and
extractables and a  pyrolysis test to
measure general composition.
                                     Results and Conclusions
                                       The  project was concerned  princi-
                                     pally with the chemical compatibility of
                                     materials as measured by the liner's ab-
                                     sorption of the waste solution, changes
                                     in mechanical properties, and (in some
                                     cases) changes in permeability. Results
                                     indicated that some of the liner mate-
                                     rials performed satisfactorily in contact
                                     with certain wastes. But because waste
                                     combinations can be highly specific,
                                     compatibility testing is needed to select
                                     a liner for a given waste.

                                     Lining Materials

                                     Soil Liner
                                       Specimens of the native soil liner per-
                                     formed quite satisfactorily during  the
6.5 years of exposure to each of the six
waste   liquids—low-alkalinity   waste
(spent caustic), lead waste, oily wastes
(slurry oil and Oil  Pond 104), and pes-
ticide waste. Combinations of the soil
liner with the acidic wastes were elimi-
nated in the screening tests because of
apparent incompatibility.
  With all wastes,  the 1-ft-thick soil lin-
ers showed low permeability (2.0 -  3.1
 x 10~8 cm s~1), which they maintained
throughout the exposures. The appar-
ent insensitivity of the native soil to
various chemicals  is probably related to
its high ratio of nonclay to clay minerals
in  the  fraction smaller than  2 jxm.
Another feature of this soil that may
contribute to its insensitivity is the high
salt content (it had been dredged from
the channels in the Carquinez Straits in
California and had dried on land). Ex-
cept for the possible migration of cop-
per, the other five metals tested (cad-
mium, chromium,  lead, mercury, and
nickel) did not appear to migrate more
than 2 cm (0.8 in.) into the liner during
958 days of exposure to Oil Pond 104,
which contained these trace metals.

Asphalt Cement
  Combinations of the asphalt concrete
and the oily wastes were eliminated in
the screening tests. But in spite of the
low permeability and good mechanical
properties for the 6.4-cm- (2.5-in.-)thick
asphalt concrete, the liner was deficient
in several other exposures. Both speci-
mens leaked when in contact with the
strong acid (HNO3-HF-HOAc). Some of
the aggregate at the  surface was dis-
solved, and the asphalt itself hardened
severely during exposures  that were
relatively short (40 and 199 days). Leaks
also developed in the specimens below
the spent caustic and  lead wastes. The
lead waste contained sufficient oily con-
stituents to cause  the asphalt concrete
to become almost  a slush. Some seep-
age also occurred through  the  speci-
mens below the water. We conclude
that this type of lining material should
not be used with  wastes  that contain
oily compounds and that thorough test-
ing of  the aggregates is  necessary.
Also, a thickness of 6.4 cm (2.5 in.) may
be insufficient even for water and com-
patible dilute wastes.

Bentonite and Sand Mixtures
  Polymer-treated  bentonite and sand
mixtures were tested in cells containing
the lead, pesticide, slurry oil, and Oil
Pond 104 wastes. These liners had been

                                                                                Ot/fer flaff-
Figure 2.    Exposure rack loaded with polymeric membrane specimens. The rack is exposed at a
           45° angle to the south.
Figure 3.   Open exposure tubs lined with polymeric membranes and partially filled with haz-
           ardous wastes. The tubs were covered with chicken wire and placed in a shallow
           basin lined with an elasticized polyolefin membrane. During rainy weather, these
           cells were protected by a corrugated plastic cover.
eliminated from exposure with the acid
and  strong  alkaline  wastes  in  the
screening  test.  The 13-cm-(5-in.-)thick
specimens exhibited  low permeability
(<10~8 cm s"1), though the bentohite
A   specimens   showed  significantly
lower permeability than the  bentonite
B specimens. This type of lining mate-
rial is probably not satisfactory for oily
wastes, since considerable fingering of
                                                              Deionized Water
                                                              in Outer Bag
                                                                Inner Pouch-
                                                                Under Test
                                                                  Waste Liquid
                                                                   jn the Inner
                                                                                Figure 4.    Schematic of a pouch assembly
                                                                                           showing inner pouch made of
                                                                                           membrane material under test.
                                                                                           The pouch is filled with waste
                                                                                           liquid and sealed at the neck.
                                                                                           The  outer  polybutylene  bag,
                                                                                           which can be easily opened, is
                                                                                           filled with deionized water.
the waste into the liner mass took place
during the 980 days of exposure. None
of the oil broke through the liner to be
collected in the base, however. Even
though some flow through the liner oc-
curred, the distribution of the metals at
the various depths was uniform. The
use of a soil cover on the liner to pro-
duce an overburden could probably re-
duce the fingering effect and reduce the

Soil Cement
  The 10-cm- (4-in.-)  thick soil  cement
specimens showed resistance to spent
caustic, the lead waste, the two oily
wastes, and the pesticide waste. Soil ce-
ment had been  eliminated from expo-
sure to the strong acid waste (HNO3-HF-
HOAc) in the screening test. No seep-
age occurred in and of the specimens.
In the five that were  recovered and
tested,  actual  increases  occurred  in
compressive strength. Metal concentra-
tions  were uniform through the depth
of the liner.

Sprayed-On Asphalt
  When exposed to spent caustic, pes-
ticide waste, and water, the sprayed-on
asphalt showed good performance. A
leak developed in one of the specimens
in a cell containing brine. The sprayed-
on asphalt  had been eliminated from
exposure to the oily and  the highly
acidic wastes during  screening. In con-
tact with the lead waste, it has softened
considerably. In all cases, it absorbed
water. Compatibility  tests would thus
be  appropriate  when   considering

 sprayed-on  asphalt for any impound-
 ment  linings, and  all  oily or highly
 acidic wastes should be avoided.

 Polymeric Membranes
  Among  the  polymeric  materials,
 those that  were  partially  crystalline
 showed the least absorption of wastes
 and largely retained their physical prop-
 erties best. These  materials included
 sheetings  of  elasticized  polyolefin,
 polyester elastomer, high- and low-den-
 sity  polyethylene,  polybutylene, and
 polypropylene. The last four of these
 were not compounded for use as spe-
 cific liner membranes  but were tested
 because  of their potential use in liner
 materials.  Some of  these materials
 showed  considerable  swell  in  oily
 wastes. Also, important properties were
 lost when elasticized polyolefin was ex-
 posed to the highly alkaline waste (slop-
 water) and when polyester elastomer
 was exposed to the  highly acidic waste
  Polyvinyl chloride (PVC)  membranes
varied considerably from  sample to
sample and were highly variable in the
wastes. The need for compatibility test-
ing was quite apparent. Test results for
the specific materials tested varied from
major weight  losses to significant in-
creases,  and  from near embrittlement
to severe softening.  This variation indi-
cated the effects  of compound differ-
ences (e.g., plasticizers).
  Crosslinking normally causes a poly-
mer to swell less and be more resistant
to change in liquids. This  quality was
observed in the chlorinated polyethy-
lene (CPE) lining materials, which in all
but one case experienced less swelling
and fewer  property changes with the
crosslinked  materials.  In  contrast, a
thermoplastic  ethylene propylene rub-
ber (EPDM) sheeting had  significantly
lower  swelling in the wastes than a
crosslinked EPDM, which is the usual
type of EPDM sheeting used for liners.
Recognize, however, that considerable
differences do exist in the EPDM rub-
bers,  some of which can be crystalline
and would reduce swelling.
  Two membrane liners showed dis-
tinct   incompatibility   with   specific
wastes, though the  time to failure was
about 1 year. The polyester elastomer
in  the strong acid (HNO3-HF-HOAc)
failed completely and cracked. The elas-
ticized polyolefin  absorbed considera-
ble amounts  of the alkaline slopwater
waste and showed a major increase in
permeability after about 1 year in the
pouch test.
  In  order of their overall detrimental
effects on the lining materials, the 13
wastes and test media used in the proj-
ect can be grouped as follows:

  Acidic wastes
  Alkaline wastes
  Brine and industrial wastes
  Lead waste
  Oily wastes
  Trace organic test liquid
  Deionized water and pesticide waste
The  more acidic and the more alkaline
wastes of the various groups were the
more aggressive to the lining materials.
  Among the wastes included  in  the
program, those with  oily  constituents
generally caused the greatest swelling
and loss in properties. In the case of the
PVC membrane, however, two nonoily
wastes caused  significant  loss of plas-
ticizer  and thus stiffening of the PVC
  A trace (<0.1%) of an organic species
such as tributyl phosphate in an aque-
ous solution can cause severe swelling
and loss of physical  properties of some
membrane liners after long  exposure.
Considerably varied reactions occurred
among the 16 membranes  immersed in
the  tributyl  phosphate solution.  Par-
tially crystalline materials showed  the
fewest effects of the trace organics in
the wastes.
  Nonhomogeneity  of the wastes and
the sampling can pose major problems
in the compatibility testing and selec-
tion of lining materials for a given facil-
ity. More laboratory  data are  needed to
develop background correlations with
field exposure and actual service. Some
of the wastes stratified so that the waste
at the bottom of a  cell or tank had a
considerably   different  composition
from that at  the top. Thus the speci-
mens exposed  horizontally at the bot-
tom  of a cell were not exposed to the
same waste that suspended specimens
were exposed to at the top. Such could
also be the case with a pond liner when
exposure at the bottom  is compared
with exposure near the top. Thus the
possibility exists that a test specimen in
a compatibility test may not be exposed
to a  representative waste from the im-
poundment or to a waste from a critical
area in  the pond. Two of the wastes
were saturated with salts  that crystal-
lized out of the waste onto the liner,
thus exposing the liners to wastes dif-
ferent from those in the waste solution.
Constant agitation of a nonhomogene-
ous waste during a compatibility test
may be a solution, but it may not result
in the worst exposure condition. A pro-
cedure  using  agitation  should  be
Test Methods
  The various test  methods used re-
vealed significant  differences  among
the liners for each type of waste. Gen-
erally,  a correlation appears to exist
among  the  results of the different
methods used.
  Test duration should be as long as
possible. The 12- and 24-month expo-
sures originally set  in the contract are
far too short for estimating service lives
unless the latter are relatively short.
Also, the number of exposure  periods
was inadequate for  projecting some of
the physical properties because of in-
herent sources of error arising from the
nature of these tests. The  primary and
immersion tests performed in this proj-
ect were inadequate because they gen-
erally  included  only  two  exposure

Immersion Test
  An immersion test can be adapted for
use  as a compatibility test of a lining
material with a given waste if  at least
four time exposures are  used  with  at
least 1 month between exposures. But
additional investigation of the  immer-
sion test should be  run to  develop cor-
relation with actual experience.

Tub Test
  The tub test demonstrates that differ-
ent locations within an impoundment
can  have significantly different effects
on the retention of properties by a liner.
This test also shows the greater severity
of effects on liners  at the  interface be-
tween the waste and the weather.

Pouch Test
  The pouch test used in this project
with only thermoplastic and crystalline
membranes shows considerable prom-
ise for assessing the effects of a waste
liquid in contact with a polymeric mem-
brane liner. Efforts should be under-
taken to increase the applicability of this
type of test to crosslinked sheeting and
to stiff, thick sheetings. The test was run
primarily with  thinner sheetings that
could  be   heat-sealed   or  solvent-
seamed. The pouch tests, however,
may  have  to  be  run for  extended
periods of time to observe long-term ef-
fects, and they may require interpreta-
tion  until they have been used exten-

  The full report was submitted in ful-
fillment of Contract No. 68-03-2173 by
Matrecon, Inc. under the  sponsorship
of the U.S.  Environmental Protection
H. E. Haxo, Jr., Roberts. Haxo. Nancy A. Nelson. PaulD. Haxo, Richard M. White,
  and Suren Dakessian are with Matrecon, Inc., Oakland, CA 94623.
Robert Landreth is the EPA Project Officer (see below).
The complete report, entitled "Liner Materials Exposed to Hazardous and Toxic
  Wastes," (Order No. PB 85-121 333; Cost: $23.50, subject to change) will be
  available only from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 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
                                                                         ifd. S. GOVERNMENT PRINTING OFFICE: 1985/559-111/10770

United States
Environmental Protection
Center for Environmental Research
Cincinnati OH 45268
   PERMIT No. G-35
Official Business
Penalty for Private Use $300
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