United States        Off ite of 3oljd Waste (WW-562)
            'Environmental Protection    Washington DC 20460
            Agency          Order No. 731

            December 1978
v>EPA     Use of Liner
            for  Land Disposal

EPA is charged by Congress  to protect the  Nation's  land,  air,  and
water systems.  Under a mandate of national  environmental  laws
focussed on air and water quality, solid waste  management and  the
control of toxic substances,  pesticides, noise  and  radiation,  the
Agency strives to formulate and implement  actions which  lead to  a
compatible balance between  human activities  and the ability of
natural systems to supoort  and nurture life.



                 Allen  J.  Geswein

                Robert  E.  Landreth


                   Henry Haxo,  Jr.
    Presented at the  71st Annual Meeting of the

       American Institute of Chemical Engineers

               November  12-16,  1978

                                     -—»  i •••-.,• ,~i"-i-I^TI 1

                                              .. ,-.-oet



      Robert E. Landreth,* Allen Geswein,-*- and Henry Haxo, Jr.*

     The U.S. Environmental Protection Agency currently administers

eight environmental laws, one of which is the Resource Conservation

and Recovery Act of 1976  (RCRA).  Among the several major objectives

of RCRA is the elimination of improper land disposal practices, i.e.,

those disposal practices and sites identified as environmentally

unacceptable according to EPA's proposed criteria issued pursuant

to the Act.  The criteria cover all forms of disposal of wastes on

landfilling, landspreading, and impoundment or lagooning and apply

to residential and commercial as well as industrial wastes.

     Under RCRA's mandate, EPA has undertaken the research and

development of environmentally safe practices for disposal of

industrial residues.  Industrial residues can be disposed of in

an environmentally safe manner with carefully selected and designed

secured landfills.  Properly designed secured landfills can prevent

excessive seepage of potential pollutants into the surrounding soils

by use of liner materials.  Desirable properties of liner materials

for surface impoundments should be (1) impermeable to wastes;  (2)

durable; (3) resistant to chemical, biological, and mechanical

damage, weathering, and deterioration; (4) low in cost; and  (5)

easy to install.  The disposal of residuals in landfills requires
* Solid and Hazardous Waste Research Division, Municipal Environmental
  Research Laboratory, U.S. Environmental Protection Agency
+ Land Disposal Division, Office of Solid Waste, U.S. Environmental
  Protection Agency
# President, Matrecon, Inc.

an understanding of these factors, since not all candidate liner

materials have these desirable properties.

     The Solid and Hazardous Waste Research Division of the

Municipal Environmental Research Laboratory, U.S. Environmental

Protection Agency, has developed research projects designed to

answer questions for the user community and develop documents which

will aid in the understanding of surface impoundment design.  These

research projects have been developed to assimilate or expand on

existing data and generate new data.  This data base will be used

to establish evaluation criteria and test protocol for liner

materials.  The overall objectives of these research projects are

to determine the effects of waste leachate on the physical pro-

perties of liner materials, to develop a data base from which the

potential life of the material can be predicted, and to develop

economic data on the materials and associated construction costs.


     Those materials that can be listed as potential liner candidates

include natural clay soils; admixed materials (e.g., soil cement

and asphaltic compounds); polymeric membranes; and sprayed-on •

materials.  Each of these broad liner classifications have advantages

and disadvantages when used as containment material.  They are,

however, being used to contain a wide variety of residuals.  The

liner materials being researched, excluding clays, are listed in

Table 1.  Clay materials are being evaluated in soil attenuation




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Natural Soils

     The natural clay soils have been used to contain a variety of

industrial wastes.  Clay liner designs are usually based upon

permeability and sorption.  Permeabilities of clays range from

10-5 cm/sec to 10-8 cm/sec.  In layers of several feet thick, clays

could offer only minimal seepage rates for several hundred years.

Industrial waste ponds have clay liner thicknesses in the 2-70

ft range.  Obviously, where a toxic waste is being contained,

a greater depth of clay would be required.

     Adsorption and ion exchange are two principle mechanisms where

clays act as passive barriers.  While these two principles are

different, -hey are difficult to distinguish because each results

i.a uptake ^r,C both can occur simultaneously.  The literature on

these mechanisms is extensive.-'-  Data on the sorption of industrial

waste and municipal sanitary landfill leaichate are being generated

in a series of controlled laboratory studies.

     One effort2 is examining the factors that attenuate contaminants

(limit contaminant transport) in leachate from municipal solid waste

landfills.  These contaminants are:  arsenic, beryllium, cadmium,

chromium, copper, cyanide, iron, mercury, lead, nickel, selenium,

vanadium, and zinc.  The general approach is to pass municipal

leachate, as a leaching fluid, through columns of well-characterized,

whole soils maintained in a saturated anaerobic state.  The typical

municipal refuse leachate is spiked with high concentrations of

metal salts to achieve a nominal concentration of 100 mg/1.  The

most significant factors in contaminant removal are then inferred

from correlation of observed migration rates and known soil and

contaminant characteristics.  This effort will contribute to the

development of a computer simulation model for predicting trace

element attenuation in soils.  Modeling efforts to date have been

hindered by the complexity of soil-leachate chemistry.

     The second effort-^ in this area is studying the removal of

contaminants from landfill leachates by soil clay minerals.  Columns

are packed with mixtures of quartz sand and nearly pure clay minerals.

The leaching fluid consists of typical municipal refuse leachate

without metal salt additives.  The general approach to this effort

is similar to that described in the preceding effort except that

(a) both sterilized and unsterilized leachates are utilized to

examine the effect of microbial activity on hydraulic conductivity

and (b) extensive batch studies are conducted of the sorption of

metals from leachate by clay minerals.

     A third effort relates to organic contaminant attenuation by

soil.   This is our initial effort in organic contaminant movement

in soil.  Much more is known about inorganic contaminant movement

in soil because the analytical techniques for inorganic materials

are well developed and relatively cheap compared to the time-consuming

analytical techniques for organic materials.  The problem is com-

pounded by the fact that organic contaminants are more numerous

and more are being synthesized all the time.  PCB is the organic

contaminant currently being investigated.  As a part of the above-

described effort, a gas chromatographic analytical procedure was

developed that allowed improved quantitative measurement of PCB's

in aqueous solutions.

Admixed Materials

     Admixed materials, such as soil cements and asphaltic concrete,

have also been used to line containment ponds, but to a lesser

degree.  While these materials do have application for containment

based upon permeability, the potential chemical interaction limits

the type of residuals that can be contained.  W. S. Stewart** reported

that the advantages of asphalt materials are their availability,

versatility in available physical forms, and use for large-scale

waterproof construction.  Pure asphalt has also been used in a

membrane form.  The major disadvantage to the asphalt membrane was

the subgrade requirement, weathering, aging and erosion from

turblent water, and damage from mechanical equipment.  Stewart

developed a matrix based upon the chemistry of the liner and the

waste stream  (Table 2).  This table should only be used as a starting

point.  Actual exposure tests should follow to determine specific


     Asphalt linings, compacted properly, have permeabilities in

the range of 10-7 cm/sec.  The Asphalt Institute  (College Park,

Maryland) has conducted tests in their laboratory^ showing

that properly designed mixes can be essentially impermeable

to water  (k=o).  The chemical resistance of asphaltic materials

should be checked first, by immersion tests or other test

procedures.  Jharts have been developed which illustrate

resistance of asphalt.  Strength of waste streams and temperature




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may have an effect on the lining and deserves further laboratory

testing before selection.  In those admixes where stone/gravel

are used, the chemical resistance of the stone/gravel should

also be determined.  Dissolution of the stone/gravel will seriously

affect the integrity of the liner and could cause direct

channeling through the liner.

Flexible Membrane Liners

     Flexible membrane liners are becoming increasingly popular for

containment devices.  Their relative ease of installation and the

chemical resistance to a wider variety of chemicals lend themselves

to increased use by industry.  EPA research efforts are underway

where a range of generic type materials and thicknesses are being

exposed to selected industrial wastes.

     Two projects have been previously reported.6  Data from the

first year's exposure of municipal landfill leachate on flexible

membranes and admixed materials resulted in relatively little change

to the liners.7  There was no apparent increase in permeability

in any of the liner materials.  There were losses in compressive

strength of the admixed materials and in physical properties of

some of the polymeric membranes and swelling of most membranes.

     Due to the relative small change in the first year, the

exposure time has been increased to a total exposure time of 56

months  (July 1979).  In addition to the longer exposure time,

additional subtasks have been added to increase the overall data


     A series of swelling tests8 at room termperature and at 70°C

indicate that membranes of neoprenes, chlorosulforated polyethy-

lene, and chlorinated polyethylene continually swell in water, where

as the polyethylene, polybutylene, polyester, and elasticized

polyolefin reach a plateau in the swell, as did polyvinyl chloride.

In the permeability tests there was some indication that permeability

increases with time, probably due to the swelling of the membranes

by water.  Since permeability tests take a long period of time, due

to the extremely low coefficient of permeability, data are still

being collected.  Also, with the increased attention of landfill

gag migrating away from the land disposal sites, gas permeability

data are being collected.  Data will be complete and reported on

in a final report, scheduled for October 1979.

     The second project was recently updated,' and a complete report

is due in late 1978.  The results of the study must still be con-

sidered preliminary at this point in the exposing testing, but it

is quite apparent that some of the hazardous wastes can seriously

affect the physical properties of the lining materials.  The waste

streams are bein/g' completely characterized to determine individual

components which may be aggressive toward linings.  Generally,

organic constituents tend to have solvent effects upon the organic

polymeric membranes and asphaltic materials.  The effect will depend

upon the specific component, strength, and liner material.

Spray-On Materials

     A third effort10 relates to the types of materials being tested

for use as liners for sites receiving sludges generated by the removal

of sulfur oxides (SOX) from flue gases of coal-burning power plants.

The volumes of SOX sludge generated in any particular place will,

typically, be much greater than those for other types of wastes, and

therefore the disposal sites will be large.  Consequently, methods

of lining such disposal sites must have a low unit cost.  It is

desirable that the materials be easy to apply or install.  Because

of these considerations, the number of polymeric membranes included

in the study have been reduced, whereas admixed and sprayed-on

materials are being emphasized.  A total of 18 materials are being

tested, with two types of Flue Gas Desulfurization (FGD) sludges.

The sludges are from an eastern coal-, line-, and limestone-scrubbed



     The construction of a lined solid waste disposal facility

requires the close attention of the field engineer.  The best

specification can be negated if the installation of the liner

system is improperly monitored in the field.  Three distinct phases

of construction are necessary to complete the proper installation

of a liner.  Each phase requires attention if a successful contain-

ment is to be built.  These three phases are discussed separately.

Subgrade Preparation

     The liner, which is a relatively thin barrier, must rest on a

firm, smooth foundation.  Ideally, the subgrade would consist of

1 to 2 feet of compacted coarse-grained material, such as sand.

The maximum grain size of the material is somewhat dependent upon

the liner material to be used.  If recompacted or imported clay is

used or if the in-situ soil is to be amended by the addition of

cement or montmorillonite, a larger grain size in the subgrade can

be tolerated because the barrier will be thicker than polymeric

membranes or asphaltic compositions.  There are no specific recommenda

tions for maximum grain size, but it would seem logical that a clay

liner that is 12 to" 18 inches thick could easily tolerate stones

as large as 1 inch in diameter in the subgrade.  Polymeric membranes

should have a maximum grain size smaller than this, and specifications

have been written which call for 100 percent of the subgrade to pass

a no. 4 sieve.

     In all cases, the subgrade should be free of roots, branches,

and other similiar materials which could puncture the liner.  Also,

organic material can degrade and give off methane and other gases

which could be trapped under the liner and could eventually rupture

the barrier.

     The subgrade should be smooth.  The thin liner materials should

not be required to bridge over tire tracks and other depressions.

T?he subgrade can be rolled or dragged to achieve an acceptable

sybgrade texture.

     The subgrade can be susceptible to differential settlement if

not properly compacted.  Obviously, the field inspection should

include soil tests to ensure optimum compaction of the subgrade.

Liner Installation

     Most liner materials require a unique installation technique.

The exception is the polymeric materials which use essentially the

same installation procedures.  The following is a brief discussion

of how to install paving asphalt, hot-sprayed asphalt, asphalt

emulsion sprayed on polypropylene fabric, polymeric membranes,

montmorillonite, and soil-cement liners.  Standard specifications

for the liner materials are available and give more detail on tfte

proper installation procedures.

     Paving asphalt is placed by a conventional paving machine.  If

a sealer coat is specified, it can be applied using a truck equipped

with a spray bar or by using a hand-held sprayer.  Since the integrity

of this type of liner can be damaged by weeds growing through it, the

use of a soil sterilant on the subgrade to prevent plant growth may

be required.

     Hot-sprayed asphalt membranes are constructed using a spray bar.

The completed membrane will consist of 1 1/2 to 2 gallons of sprayed

asphalt per square yard and can range in thickness from 1/4 to

3/4 of an inch.  Three or four passes of the spray bar are used to

build up this membrane.  If fewer passes are used (higher application

rate per pass), there is a tendency for bubbles to form.  Leaks

will develop when these bubbles ruptures.  Joints are formed by

overlapping.  The specified overlap varies from 1 to 12 inches.

     There is a three-stage construction process for the asphalt

emulsion sprayed on polypropylene fabric.  First the fabric is

spread on the ground.  The fabric is in sheets 15 feet by 300

feet which are sewed together.  A mixture of water, a wetting

agent, asbestos, and an asphalt emulsion is then sprayed in two

coats.  The first coat is applied at a rate of 1 gallon per square

yard.  When this coat dries, the evaporation of the water causes

pinholes to develop in the membrane.  A second coat of the mixture

is spjuyed at a rate of 0.4 to 0.5 gallons per square yard.  The

final membrane is approximately 100 mils thick  (one mil equals

0.001 inch).  The manufacturer does not recommend placing this

membrane when the temperature is below 40 degrees F.

     Plastic and rubber membranes are delivered to the site in

large sheets.  These membranes range in thickness from 10 to over

60 mils.  Typically, these sheets will have many factory splices

in the material.  In order to make the liner watertight, a number

of field splices are required.

     Anchoring the edges of plastic and rubber membranes is accom-

plished by burying the edge in a shallow trench.

     The construction of a sanitary landfill liner using montmoril-

lonite as an admixture to the native soil is accomplished using

conventional farm and earth-moving equipment.  Spreading the

grayishwhite granular material can be ;',:ooraplished with a fertilizer,

pesticide,, or manure spreadec.  Typica^ application rates range from

10 to 20 pounds per square yard.  Some experimentation may oe required

to determine the proper setting to use for a particular spreader.

After the material is spread, three to four passes with a disk are

required to mix the montmorillonite to the appropriate depth, usually

6 inches.  Flat steel-wheeled rollers or rubber-tired rollers are

recommended for compaction.  The use of Sheepsfoot rollers are

not recommended by the manufacturer because these devices tend to

force the montmorillonite deeper into the subgrade than 6 inches.

The material is not an effective liner if it is placed deeper than

the design depth.

     Soil-cement is a mixture of pulverized soil and measured amounts

of Portland cement and water, compacted to high density.  Since no

full-size sanitary landfill liner has been built using this material,

no special construction techniques have been developed.  In general,

soil-cement pavements are built using the following steps:


(1) spread portland cement and mix, (2) apply water and mix,  (3)

compact the mixture, (4) perform final grading for drainage, and  (5)

cure the mixture.  Depending upon the soil type encountered, cement

is added at a rate of 3 to 20 percent of the weight of the soil.

Spreading and mixing devices have been designed specifically for

soil-cement pavement construction, but conventional earth-moving .

equipment can be used.

Liner Protection

     No liner material should be used as a pavement.  While some of

these materials can easily support rubber-tired construction equip-

ment, high-wheel loading could rupture some membranes.  Equipment

with crawler treads should not be allowed to operate directly on the

liner.  Manufacturers recommend protecting the liner with an earth

cover 1 or 2 feet thick.  This material should not contain jagged

rocks or other sharp objects that could damage the liner.  Similarly,

the first lift of solid waste placed in the fill site should not con-

tain items such as bulky wastes, pipe,, or white goods that could

puncture the liner during the filling operation.  Such quality control

is difficult to achieve, considering the heterogeneous nature of solid

waste delivered in compactor trucks.

     The above construction information is very general.  In an

attempt to be more specific about the actual placement of liner

materials, a study is being undertaken to assess the best procedures

and practices used by the liner industry.  The study will encompass

the site preparation and liner placement for a variety of clay,

admixed, and polymeric liner materials.

Field Verification

     Field verification studies for determining liner material

performance require a substantial input of research dollars and

time in order to obtain a long-term data base.  The ideal field

verification study would include 20 liner materials, 20 waste

streams, exposure periods up to 5 years, and be located in four

different geographic locations.  Since studies like this are not

feasible, based on a limited budget and time constraints, an

alternative study has been selected.

     A recently completed studyll identified disposal sites where

liner materials were installed.  The survey obtained information

relating to waste type, waste depth, Waste age, type of liner

material, owner, installer, and other pertinent information on

the disposal site.  Potential methods of liner recovery and the

associated costs were discussed.

     Although these data are still being evaluated, an approach is

being developed where three to five selected lined sites will be

investigated during the next year.  Based upon the results of this

effort and the interpretation of the data, additional sites may be


Liner Listing-NSF

     In an attempt to alleviate the problem of continually reviewing

material and performance specifications from several different

companies for the same generic type polymeric material, the National

Sanitation Foundation (NSF) has initiated an effort which will lead

to a recogni2ed listing of flexible membrane liner materials.  The

NSF has gathered together representatives of Federal and State

governments, industry, manufacturers, users, and the private

community.  The purpose12  of the listing will be to:

     "Establish the necessary performance requirements for flexible
     membrane liners and covers for use in the retention and
     containment of substances so as to maintain and protect the
     environment.  The flexible membrane liners covered under this
     standard are intended to retain waters and contain pollutants
     or chemicals".

     The materials to be incorporated into this listing are

thermoplastics, thermoplastic elastomers, and elastomers.  Data

are currently being reviewed by the advisory committees.


     The vj.S. Environmental Protection Agency, under authority of

the Resource Conservation and Recovery Act of 1976  (Public

Law 94-580), is developing recommendations, criteria, and

regulations for the utilization of liner materials.  These

recommendations, criteria, and regulations are currently in

various stages of review by industry, the private sector,

and o.her government agencies.

1.   Sanks, R. L., J. M. LaPlante, and E. F.  Gloyna [Environmental
          Health Engineering Research Laboratory, University of Texas
          at Austin].  Survey suitability of  clay beds for storage of
          industrial solid wastes.  Report to Texas Water Quality
          Board.  Technical Report EHE-76-04, CRWR-128.   Austin,
          University of Texas at Austin,  June 1975.  [95 p.]

2.   Fuller, W.  H.  [Dept. of Soils, Water, and Engineering, Univer-
          sity of Arizona].  Investigation of landfill leachate
          pollutant attenuation by soils.  Environmental Protection
          Publication EPA 600/2-78/158.   Cincinnati, U.S.
          Environmental Protection Agency, Aug. 1978, 239 p.

3.   Griffin, R. A., and N. F.  Shimp [Illinois State Geological
          Survey] .  Attenuation of pollutants  in  municipal
          landfill leachate by  clay minerals.   Environmental
          Protection Publication EPA 600/2-78/157.   Cincinnati, U.S.
          Environmental Protection Agency, Aug. 1978.  157 p.

4.   Stewart, W. S.  [Exxon Research and  Engineering Company].
          State-of-the-art study of landfill  impoundment
          techniques.  Environmental Protection Publication EPA
          600/2-78/196.  Cincinnati, U.S. Environmental  Protection
          Agency, Oct. 1978.  (In press.)

5.   Chemical resistance of asphalt coatings.   Materials Protection,
          5(1):81-83, Jan. 1966.

6.   Haxo, H. E,, and R. M. White [Matrecon,  Inc.].  Evaluation of
          liner  materials exposed to leachate.  Interim  Report
          No. 2.  Environmental Protection Publication EPA
          600/2-76/255.  Cincinnati, U.S. Environmental  Protection
          Agency, Sept. 1976.  67 p.  (Distributed  by National
          Technical Information Service,  Springfield, Va.,  as
          PB-259 913.)

7.   Haxo, H. E., R. S. Haxo, and R. M. White [Matrecon, Inc.].
          Liner  materials exposed to hazardous and  toxic sludges.
          Interim Report No. 1—Mar. 1975-Oct. 1976.  Environmental
          Protection Publication EPA 600/2-77/081.   Cincinnati, U.S.
          Environmental Protection Agency, June 1977.  75 p.
          (Distributed by National Technical  Information Service,
          Springfield, Va., as  PB-271 013.)

8.   Haxo, H. E., R. S.  Haxo, and T. F. Kellogg.   Evaluation of liner
          materials exposed to leacbate.  Interim Report No. 3.
          Cincinnati, U.S.  Environmental Protection Agency, August
          1978.   69 p.  (Unpublished draft report, EPA Project
          68-03-2134.)  (in press.)

9.   Haxo, H. E. [Matrecon, Inc.].   Interaction of selected lining
          materials with various hazardous wastes.  In D. W. Shult2,
          ed^. Land disposal of hazardous wastes, Proceedings; 4th
          Annual Research Symposium, San Antonio, Tex., Mar. 6-8,
          1978.   Environmental Protection Publication EPA
          600/9-78/016.   Cincinnati, U.S. Environmental Protection
          Agency,  p.256-272.

10.  Fry, Z. B., and C.  R.  Styron.   Liner materials exposed to flue
          gas cleaning sludges.  Interim Report  No. 1.  (Unpublished
          draft  report,  EPA Project IAG-D5-0785.)  (In press.)

11.  Ware, S. A., and G. S. Jackson.  Liners for sanitary landfills
          and chemical and hazardous waste disposal sites.
          Environmental  Protection  Publication EPA 600/9-78/005.
          Cincinnati, U.S.  Environmental Protection Publication, May
          1978.   92 p.

12.  Personal communication, R. E.  Landreth to G. W. Sherlaw,
          Standards Development, National Sanitary Foundation, Ann
          Arbor, Mich.,  May 17, 1978.
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