United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-169 Jan. 1985
Project Summary
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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).
Introduction
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
years).
2. To determine the durability and
cost effectiveness of polymeric
membranes, sprayed-on mem-
branes, admixed materials, and
natural soils as liners for hazard-
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ous waste storage and disposal
facilities.
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
facilities.
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
wastes.
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-
ever).
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
were:
• One compacted soil of low permea-
bility
• 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
fabric
• Thirty-two different commercial
polymeric sheetings based on the
following polymer types:
Butyl rubber
Chlorinated polyethylene
Chlorosulfonated polyethylene
Elasticized polyolefin
Neoprene
Polybutylene
Polyester elastomer
Polyethylene (low- and high-den-
sity)
Polypropylene
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
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Top Cover
Epoxy
Coating-~"
Caulking
Bolt
Steel Tank
Outlet Tube with
Epoxy-Coated
Diaphragm
Top Cover
Epoxy
Coated
Epoxy Grout Ring
Admix Liner
Waste Column:
•—10"x15"x12" High
Outlet Tube with
Epoxy-Coated
Diaphragm
Bolt
Flanged Steel
Spacer
Glass Cloth
To
Collection
Bag
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
days.
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
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Ot/fer flaff-
Polybutylene
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-
Membrane
Under Test
Waste Liquid
jn the Inner
Pouch
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
flow.
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
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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
(HNO3-HF-HOAc).
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.
Wastes
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
specimens.
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
studied.
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
periods.
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-
sively.
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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
Agency.
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
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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