EPA/600/A-92/050
THE ENVIRONMENTAL PROTECTION AGENCY'S MUNICIPAL SOLID WASTE
LANDFILL LINER DESIGN CRITERIA
Robert E. Landreth
Chief
Municipal Solid Waste and Residuals Management Branch
Risk Reduction Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
INTRODUCTION
The soon to be published non-hazardous land disposal
regulation, RCRA sub title D (40 CFR Parts 257 and 258) must'
achieve three objectives. The first is to be protective of human
health and the environment, second to be flexible so as not to
stifle innovative designs, and third to allow individual states
the latitude to develop state specific regulations. The
containment systems (liners) currently under consideration will
achieve these three goals. This paper will briefly discuss the
approach to the liner design. Additional information will be
forth coming as final decisions are made.
Statement of Proposed Regulation
While the regulations are still being finalized, the
containment systems are being focused on two approaches. The
first is a generic design. This design has a composite liner
system that is designed and constructed to maintain less than 3 0-
cm depth of leachate over the liner. The second approach consists
of liners and leachate collection systems to ensure that the
concentration values of selected chemicals will not be exceeded
at some point of compliance. Both of these approaches require
additional discussion to define terminology and to provide
guidance on how to comply with the two approaches.
A composite liner shown schematically in Figure 1, is
defined as consisting of two components; the upper component is a
flexible membrane (FML) with a minimum ofo.75mm (30 mil)
thickness, the lower component consists of at least a 60 cm (24
inches) layer of compacted soil with a hydraulic conductivity
less than or equal to 1 x 10"7 cm/sec. The required thickness
will depend upon the site-specific design, installation/
construction concerns, seamability and long-term durability.
Taking these factors into account, the EPA recommends the
following minimum FML thickness for landfill bottom liners:
polyvinylchloride (PVC)-0.75mm (30 mil), chlorinated polyethylene
(CPE)-0.75mm (30 mil), reinforced chlorosulfonated polyethylene
(CSPE-R)-0.9mm (36 mil) and semi- crystalline polyethylene (PE)-
1.5mm (60 mil). The FML component must be installed in direct and
uniform contact with the compacted soil component so as to
minimize the migration of leachate through potential defects in

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the FML. A leachate collection and removal system (LCRS) should
be located immediately above the composite liner to control the
level of leachate on the liner.
The point of compliance is defined as that point in the
uppermost aquifer at the waste management unit boundary. The
Director of an approval state may re-define the point of
compliance after considering the hydrologic characteristics of
the facility and surrounding land, the quantity and quality of
the leachate, the quantity , quality and flow of the groundwater,
the proximity of groundwater users, the practical capability of
the owner/operator and the public health and the environment.
Generic Design Considerations
As mentioned previously the generic design has two major
components: the leachate collection and removal system and the
composite liner system. The leachate collection system should be
designed to meet the performance criteria standard of maintaining
less than a 30 cm head above the liner. Leachate refers to any
waste contacted by water including rainfall and snowmelt that
combines with liquid in the waste and moves by gravity to the
bottom of a landfill facility. Leachate quality, defined by the
concentration of its constituents and water quality parameters
(such as COD, BOD, pH, and eH), changes with time as the landfill
matures. During the course of landfilling activities, waste
characteristics may also change, producing profound changes in
the type of leachate produced. As such, leachate is both site
specific and waste specific with regard to both its quantity and
quality.
Leachate is generally collected and removed from the
landfill through sand blanket drainage layers, synthetic drainage
nets, and perforated plastic pipes. Each LCRS consists of the
following components:
A low-permeability base which is either a soil
liner , composite liner, or flexible membrane
liner (FML);
A high-permeability drainage layer constructed of
either natural granular materials (sand and
gravel) or synthetic drainage material (geonet)
which is placed directly on the flexible membrane
liner, or its protective bedding layer;
Perforated leachate collection pipes within the
high-permeability drainage layer to collect
leachate and carry it rapidly to the sump or
collection header pipe;
A protective filter material surrounding the
pipes, if necessary, to prevent physical clogging
of the pipes of perforations;
A leachate collection sump, sumps, or header pipe
system where leachate can be removed;
A protective filter layer over the high-
permeability drainage material which prevents

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physical clogging of the material; and
A final operational protective layer of material
that provides a wearing surface for traffic and
landfill operations.
The recommended bottom liner slope is two percent at all
points in each system. This slope is necessary for effective
gravity drainage through the entire operating and post-closure
period. The settlement estimates of the foundation soils
performed during design should set this two percent grade as a
design objective. It may be necessary to initially design the
slopes steeper than two percent to allow for settlement.
The high-permeability drainage layer is placed directly over
liner or its protective bedding layer. Often the selection of
drainage material is based upon the availability of natural
granular materials at the site. In some regions of the country,
hauling costs may be very high for sand and gravel or appropriate
materials may be unavailable and the designer may elect to use
geosynthetic drainage nets (geonets) or synthetic drainage
materials as an alternative. Frequently, geonets are substituted
for granular materials on steep sidewalls since maintaining sand
on the slope during construction and operation of the landfill is
difficult.
FML Component
The design of the FML component of the composite liner
system considers the technology guidance, material stress
consideration, structural details and panel fabrication.
Technology Guidance: To achieve EPA guidelines for minimum
leakage, the liner should not leak at a rate greater than the
action leakage rate (ALR) stated in the site's response action
plan as determined by the owner/operator and the permit writer.
The minimum thickness of FML is set at 0.75mm (30 mils). State
requirements may be more stringent than EPA guidelines; the more
stringent requirements must be followed in design. It should be
noted that increasing the liner thickness can greatly increase
the cost. Increasing the liner thickness of the same material
from 0.75mm to 1.5mm (30 to 60 mils) can double the per acre cost
of the FML, the actual increase will depend on the polymer type.
Stress Considerations: Stress conditions must be considered
for both the bottom and the side slopes of a landfill. For side
slopes, the weight of the FML itself and the weight of the
overburden and waste must be reckoned with. Because the
geosynthetic must be able to support its own weight on the side
slopes, the specific gravity, thickness, and yield stress of the
material and the friction angle must be known to calculate self-
weight. For exposed FMLs, uplift forces caused by wind is another
critical loading condition. For FMLs covered with a layer of
soil, the tendency of the soil to slide down the slope is a
critical loading condition and should be evaluated. For FMLs at
the bottom of the facility, the FML should be evaluated against

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two different mechanisms by which loads can be applied. The first
mechanism is due to compression or consolidation of the
foundation soil supporting the landfill. The second mechanism is
due to compression or consolidation of the overburden and waste.
Structural Details: Anchorage, access ramps, collection
standpipes, and penetrations are all structural details that
warrant attention, especially in double liner systems.
In anchorage trenches, the geosynthetic can be ripped or
pulled out during construction, filling, and closure. The
pullout capacity for various anchorage configurations (e.g.,
trenches with box or V-shape) can be calculated. Research is
currently being conducted at Drexel University's Geosynthetic
Research Institute to evaluate this design approach.
Most facilities have access ramps to bring waste into the
landfill. With double liner systems, the continuity of both
liners must be maintained over the entire surface. Construction
activities such as traffic induced damage and site drainage must
be addressed in the design. Vertical collection standpipes are
used to access the primary leachate collection sumps. As waste
settles the standpipe can be affected by downdrag and the primary
FML beneath can be punctured. ASTM D-2435 is one dimensional
consolidation test that could be used to measure the
consolidation properties of the waste. From these properties, the
settlement of the waste can be calculated. This calculated
settlement is used to calculate the downdrag forces acting on the
stand pipe. The settlement of the standpipe due to the downdrag
forces can then be calculated to determine the impact on the FML.
Remedies could include coating the standpipe with a viscous or
low-friction coating or encapsulating it with multiple layers of
low friction resistance material. A flexible foundation or spread
footer design beneath the standpipe could provide a more gradual
transition and spread the distribution of contact pressures over
a larger portion of the FML than would a rigid foundation design.
Manufacturers have recently developed polyethylene standpipes
that are light weight, sealable,-have low side wall friction and
good chemical resistance.
Panel Layout: The layout of FMLs in the landfill should be
planned so that seams run up and down the slope and that the
length of field seams is minimized whenever possible.
Soil Component
The soil component of the composite liner must be at least
two feet thick with a hydraulic conductivity of no more than 1 x
10" cm/sec. To meet the 1 x 10~7 cm/sec requirement, other
factors including the actual construction of the soil liner
(density, strength, etc.), slope stability, settlement and bottom
heave; and long-term integrity of the liner and controls for
liner failure may need to be considered.

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Chemical Resistance
Chemical compatibility or chemical resistance to the waste
or leachate has been and continues to be a major factor in
selecting construction materials for a waste disposal facility.
The Agency has a long standing policy that all construction
materials coming in contact with leachate must be chemically
resistant to that leachate. The Agency uses EPA Method 9 09 0 or
EPA Method 9100 as the procedure to evaluate the candidate
materials.
Quality Assurance/Quality Control Testing
A quality assurance/quality control program has two
principal components. The first is the Construction Materials
Quality Control, which is designed to ascertain that materials
used meet specifications. The second component is the
Construction Quality Assurance Program which is designed to
ensure that all methods used in testing, construction and
placement of materials follow and exceed accepted practice
criteria. Combined, these element constitute the QA/QC Plan.
Quality control testing performed on materials used in
construction of the landfill include source testing and
construction testing. Source testing defines material properties
at the point of manufacturer to ensure the properties used in the
design are being met. Construction testing ensures the
appropriate material was delivered at the site.
Activities of the construction quality assurance (CQA)
officer are essential. The CQA Officer's responsibilities, and
that of the CQA's staff members, include the following:
communicating with the contractor;
interpreting and clarifying project drawings and
specification and recommending acceptance or
rejection by the owner/operator of work completed
by the construction contractor;
submitting blind samples (e.g), duplicates and
blanks) for analysis by the contractor's testing
staff or one or more independent laboratories as
applicable;
notifying owner/operator of construction quality
problems that need to be resolved on-site in a
timely manner;
observing the testing equipment, personnel, and
procedures used by the construction contractor to
check for detrimentally significant changes over
time.
reviewing the construction contractor's quality
control recording, maintenance, summarization and
interpretations of test data for accuracy and
appropriateness.

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Performance Standard Based Design
For approval of design not conforming to the minimum
technology standards of a composite liner system, the owner and
operator or the proposed municipal solid waste landfill (MSWLF)
must demonstrate that the design is protective of human health
and the environment with respect to ground water quality
downgradient from the landfill. The nature of the demonstration
is essentially an assessment the landfill leachate
characteristics, the potential for leakage from the landfill of
that leachate to ground water and an assessment of the
anticipated fate and transport of those constituents to the
proposed point of compliance at the facility. Inherent to this
type of approach, is the need to obtain sufficient site specific
data to adequately characterize to existing ground water quality,
the pre-existing ground water regime (flow direction, horizontal
and vertical gradients, hydraulic conductivity, specific yield
and aquifer thickness). The assessment must consider the effects
construction of the MSWLF may have on the groundwater system. The
major consideration here, for shallow groundwater systems, is the
local capturing of precipitation that normally would have
infiltrated as a source of groundwater recharge. An assessment
of leakage from the proposed liner and leachate collection design
should be based on empirical data from other existing operational
facilities of similar design that have the capability of leak"
detection monitoring. In lieu of the existence or availability of
such information analytical approaches based on conservative
assumptions may need to be conducted to estimate anticipated
leakage rates. Given known source concentrations, groundwater
and soil parameters, and the hydraulic gradients, a simple and
hopefully conservative assessment of downgradient concentration
at specific times and distances from the source can be conducted.
Either on dimensional or two dimensional advection/dispersion
contaminant transport methods may be used. The analysis should be
performed by qualified professionals and may entail hypothetical
computer simulations of groundwater flow and transport.
SUMMARY
The proposed municipal solid waste landfill liner
regulations are focusing on a generic design and a performance
design that will be protective of human health and the
environment, flexible enough to allow design innovative and
flexible enough to allow individual states to develop state
specific guidance. The generic design incorporates a single
composite liner with a leachate collection and removal system.
The performance design is based on selected landfill leachate
constituents not reaching the boundary (point of compliance) of
the waste management unit. Additional information and technical
guidance on the liner systems will be provided when final
decisions are made and the regulations are published.

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SELECTED REFERENCES
1.	Carroll, Jr., R.G. 1987. "Hydraulic Properties of
Geotextiles," Geotextile Testing and the Design Engineers,
ASTM 952, J.E. Fluet, Jr. Ed., American Society for Testing
and Materials, Philadelphia,, 1987, pp. 7-20.
2.	Environmental Protection Agency. 1986. "Supplementary
Guidance on Determining Liner/Leachate Collection System
Compatibility." August 7, 1986, OSWER Directive 9480.0013.
3.	Environmental Protection Agency. 1984. The Hydrological
Evaluation of Landfill Performance (HELP) Model. Vol. 1 and
2, User's Guide for Version 1. EPA/530-SW-84-009 and
EPA/530-SW-84—010. NTIS PB 85-100840 and PB 85-100832.
Municipal Environmental Research Laboratory, Cincinnati, OH
4.	Environmental Protection Agency. 1987. Minimum Technology
Guidance on Double Liner Systems for Landfills and Surface
Impoundments — Design, Construction, and Operation.
EPA/53 0—SW-8 5-014, Office of Solid Waste. Washington, DC.
5.	Environmental Protection Agency. 1987.
Prediction/Mitigation of Subsidence Damage to Hazardous
Waste Landfill Covers. EPA/600/2-87/025, NTIS PB 87-175378,
Hazardous Waste Engineering Research Laboratory, Cincinnati,
OH.
6.	"FHWA Geotextile Engineering Manual" Contract No. DTFH61-83-
C—00150, March 1985, 917 pg.
7.	Giroud, J.P. 1982. "Filter Criteria for Geotextiles,"
Proceedings. 2nd International Conference on Geotextiles,
Las Vegas.
8.	Hokanson, S., and J. Rubinson. 1988. "Liners and Leachate
Collections and Removal Systems in Double-Lined Land
Disposal Units: Future Design and Performance
Requirements." Presented at WSWMA Wastech "88, October 2 6-
27, 1988, Boston, Massachusetts.
9.	Koerner, R. M. 1990. Designing with Geosvnthetics - Second
Edition. Prentice-Hall.
10.	Landreth, Robert E. 1990. "Chemical Resistance Evaluation
of Geosynthetics used in Waste Management Applications."
Presented at ASTM Symposium on Geosynthetic Testing for
Waste Containment Applications, January 23, 1990 Las Vegas,
Nevada.
11.	Matrecon, Inc. 1988. Lining of Waste Containment and Other
Impoundment Facilities. EPA 600/2-88-052. NTIS PB 89-129670
(SW870, second revised edition.) U.S. Environmental
Protection Agency, Cincinnati, OH

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optional soil
protective cover
filter layer
waste
draimj^pipes
	low-parmeabilrty soil 	
native soil
liner system
(composite - FML on soil)
leachate collection
and removal system
(soil or geosynthetic)

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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing]
1. REPORT NO.
EPA/600/A-92/050
2.
4. TITLE AND SUBTITLE
The Environmental Protection Agency's Municipal Solid
Waste Landfill Liner Design Criteria
6. PERFORMING ORGANIZATION CODE
7. AUTHORISI
8. PERFORMING ORGANIZATION REPORT NO
Robert E. Landreth
9. PERFORMING ORGANIZATION NAME AND ADDRESS
USEPA/RREL/WMDDRD/MSWRMB
26 W. Martin Luther King Drive
Cincinnati, OH 45268
10. PROGRAM ELEMENT NO.
ii. contract/grant no.
N/A
12. SPONSORING AGENCY NAME AND ADDRESS
Risk Reduction Engineering Laboratory - Cincinnati, OH
U.S. Environmental Protection Agency (USEPA)
26 W. Martin Luther King Drive
Cincinnati, OH 45268
13. TYPE OF REPORT AND PERIOD COVERED
Published Paper
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Proceedings from the Technical Sessions of GRCDA's 28th Annual International Solid
Waste Exposition; August 20-24, 1990, Vancouver, B.C.		
16. ABSTRACT
'O The soon to be published non-hazardous land disposal
regulation, RCRA sub title D (4 0 CFR Parts 2 57 and 258) must"
achieve three objectives. The first is to be protective of human
health and the environment, second to be flexible so as not to
stifle innovative designs, and third to allow individual states
the latitude to develop state specific regulations. The
containment systems (liners) currently under consideration will
achieve these three goals. This paper will briefly discuss the
approach to the liner design. Additional information will be
forth coming as final decisions are made. ^r._	
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATi Fieid/Group
landfill, liner, municipal
f/aste, leachate, composite
liner, flexible membrane
I i ner
waste disposal
IB. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report!
UNCLASSIFIED
21. NO. OF PAGES
10
20. SECURITY CLASS (This pagel
UNCLASSIFIED
22. PRICE

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