National Waste Processing Conference Proceedings ASME 1994
FPA/BOO/A-94/246
REVIEW OF LINER AND CAP
REGULATIONS FOR LANDFILLS
ROBERT E. LANDRETH
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
Cincinnati, Ohio
ABSTRACT
The U.S. Environmental Protection Agency, through
its research and field experiences, has developed control
strategies for hazardous and municipal solid waste land-
fills and surface impoundments. These control strategies
include liner and cover systems. The liner systems include
double liners for hazardous waste and a single composite
liner for municipal solid waste. The purpose of each indi-
vidual component will be discussed with options for using
natural in-situ materials or geosynthetics. Although natural
soils are used as various components, emphasis has been
placed on the use of geosynthetics. including gcomem-
branes, geonets, geocextiles, and plastic pipes. Cover sys-
tems for both hazardous and municipal yvaste facilities are
based on a multi-layer design. The multi-layer component
characteristics, including performance, thickness and ma-
terial type will be discussed. These designs include both
natural soils and geosynthetics.
It has been demonstrated with field data that the devel-
opment of construction quality control/quality assurance
will improve the performance of the disposal facility. Cur-
rent programs and techniques used in the United States
will be discussed.
Information on design and construction has been assem-
bled into technical resource and guidance documents. The
documents present summaries of state-of-the-art technolo-
gies and evaluation techniques determined by the Agency
to constitute good engineering designs, practices, and pro-
cedures. The availability of the documents will also be
discussed.
INTRODUCTION
Waste is generated at all levels of society. This waste
may be either industry related or municipally generated.
Both types of wastes may contain a variety of potential
pollutants. In the United States of America these wastes
are managed by landfills, surface impoundments and waste
piles. The U.S. Environmental Protection Agency through
its research and field experiences have developed con-
trol strategies to prevent potential pollutants from escaping
into the environment.
The control strategies for wasie management facilities
include liner and cover systems. These systems are de-
signed for long-term performance. In addition, for those
containment systems for hazardous and toxic wastes, re-
dundancy is designed into the containment systems to help
ensure against major releases to the environment.
Field experience has clearly demonstrated that the de-
velopment of construction quality control and quality as-
surance programs will improve the waste management fa-
cility performance.
This paper will present current designs for bottom and
top containment systems, ideas and concepts for quality
control/quality assurance programs and available technical
guidance documents to support the designs and programs.
BOTTOM CONTAINMENT DESIGNS
The basic bottom liner design, for hazardous waste land-
fills, is two or more liners with a leaehate collection sys-
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FIG. 1 SCHEMATIC OF DOUBLE LINER SYSTEM.
tem above and between the liners. The redundancy aspect
of the design is that if the top liner does not perform
as designed, then the second leachate collection system
will alert appropriate personnel while corrective actions
are implemented. The bottom liner in this design is as-
sumed to contain the waste until the corrective action is
in place. The design was reviewed and modeled in satu-
rated and unsaturated hydraulic flow conditions. The result
of these studies is the current recommended design of a
double liner which has a bottom composite liner and a
top geomembrane, Figure l. The composite bottom liner
is one that consists of a geomembrane in intimate con-
tact with a compacted, low permeability natural soil. The
composite liner design has been determined to be more hy-
draulically efficient than the geomembrane or natural soil
liner working independently.
Liner Systems for Hazardous Wastes
The liner system currently being used by most haz-
ardous waste management facilities incorporates in de-
scending order a filter layer, followed by a primary
leachate collection and removal system (l.CRS), a primary
geomembrane, a leak detection, collection and removal
system (LDCRS), and a composite liner above the native
soil foundation (EPA, 1987). The composite liner is de-
fined as a geomembrane and a compacted, low hydraulic
conductivity (k < i x 10~7 cm/sec) natural soil.
In bottom liner systems for construction and field seam-
ing purposes, the geomembrane is to be at least 0.75 mm
(30 mils) thick or 1 .12 mm (45 mils) thick if left exposed
to the elements for more than 30 days. These thicknesses
may not be suitable for all geomembrane materials. The
required geomembrane thickness will depend on the site-
specific design, installation/construction concerns, seama-
bility, and long-term durability.
Liner Systems for Municipal Solid Wastes
Liner systems for municipal solid wastes may have dif-
ferent designs based on site specific considerations includ-
ing geology, hydrology and climatic conditions. Two ba-
sic approaches are used in the United States. The first is
a generic design. This design has a composite liner sys-
tem that is designed and constructed to maintain less than
Kiln* M
FIG. 2 GENERIC LINER DESIGN FOR
NONHAZARDOUS WASTE FACILITY.
30-cm (12-in) depth of leachate over the liner. The sec-
ond approach based on performance consists of liners and
leachate collection systems to ensure that the concentra-
tion values of selected chemicals will not be exceeded at
some point on the owner/operator's property.
Generic Design. A composite liner is shown schemati-
cally in Figure 2 and is defined as consisting of two
components; the upper component is a geomembrane
with a minimum of 0.75 mm (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
geomembrane thickness will depend upon the site specific
design, installation/construction concerns, seamability and
long-term durability. The geomembrane 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 the geomembrane. A leachate
collection and removal system (LCRS) should be located
immediately above the composite liner to control the leve.
of leachate on the liner.
Performance Based Design. The second design allov*,
the owner operator of the proposed municipal solic
waste landfill (MSWLF) to demonstrate that the design
is protective of human health and the environment wiifc
respect to ground water quality down-gradient from tht
landfill. The nature of the demonstration is essentially
an assessment of the landfill leachate characteristics, tht
potential for leakage from the landfill of that leachate^
ground water and an assessment of the anticipated fap
and transport of those constituents to the proposed poiN'
of compliance at the facility. Inherent to this type C
approach, is the need to obtain sufficient site specific dati
to adequately characterize the pre-existing ground wait
quality and the pre-existing ground water regime (flcv
direction, horizontal and vertical gradients, hydraOU
conductivity, specific yield and aquifer thickness). Tth
will be used to compare with data once the landfill hC
initiated activity.
TOP COVER SYSTEM DESIGNS
Proper closure is essential to complete a landfill. I
search has established minimum requirements needed
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10- 11- 94
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meet the stringent, necessary, closure criteria for both haz-
ardous and nonhazardous waste landfills in the United
States. In designing the landfill cover, the objective is to
limit the infiltration of water to the waste so as to limit
creation of leachate that might possibly escape to ground-
water sources.
The cover system must be devised at the time the site
is selected and the plan and design of the landfill contain-
ment structure is chosen. The location, the availability of
low-hydraulic conductivity soil, the stockpiling of good
topsoil, the availability and use of geosynthetics to im-
prove performance of the cover system, the height restric-
tions to provide stable slopes, and the use of the site after
the post-closure care period are typical considerations. The
goals of the cover system are to minimize further mainte-
nance and to protect human health and the environment.
Cover System for Hazardous Wastes
The closure of a hazardous waste landfill will normally
have as its main criteria the minimization of moisture
into the facility. Allowing moisture into a hazardous waste
facility will subject the waste to leaching of potentially
toxic pollutants into the leachate. Minimizing leachates in
a closed waste management unit requires that liquids be
kept out and that the leachate that does exist be detected,
collected, and removed. Where the uaste is above the
ground-water zone, a properly designed and maintained
cover can prevent (for practical purposes) water from en-
tering the landfill and, thus, minimize the formation of
leachate.
The current recommended design. Figure 3, is a multi-
layered system consisting of, from bottom to top:
• A Low-Hydraulic Conductivity Geomembnme/Soil
Layer. A 60-cm (24-in.) layer of compacted natural or
amended soil with a hydraulic conductivity of 1 x 10"7
cm/sec in intimate contact with a minimum 0.5 mm (20-
mil) geomembrane liner.
• A Drainage Layer. A minimum 30-cm (12-in.) soil layer
having a mnimum hydraulic conductivity of 1 x 1Q~2
cm/sec, or a layer of geosynthetic material having the
same hydraulic characteristics.
• A Filter Layer. A geotextile may be used to prevent soil
clogging of drainage layer. This is designed based on
soil size and vegetation layer.
• A Top, Vegetation/Soil Layer. A top layer with vegeta-
tion (or an armored top surface) and a minimum of 60
cm (24 in. ) of soil graded at a slope between 3 and 5
percent.
Because the design of the final cover must consider the
site, the weather, the character of the waste, and other
site-specific conditions, these minimum recommendations
may be altered. Design innovation is encouraged to meet
site specific criteria. For example, in extremely arid re-
1C— p«-ntp-
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C <5
05 O
a a
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<3 O ' Q
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FIG. 3 USEPA-RECOMMENDED
LANDFILL COVER DESIGN.
gions. a gravel top surface might compensate for reduced
vegetation, or the middle drainage layer might be ex-
pendable. Where burrowing animals might damage the
geomembrane/low-permeability soil layer, a biotic bar-
rier layer of large-sized cobbles may be needed above it.
Where the type of waste may create gases, soil or geosyn-
thetic vent structures would need to be included.
Cover Systems for Nonhazardous Waste
The cover system in nonhazardous waste landfills will
be a function of the bottom liner system and the liquids
management strategy for the specific site. If the bottom
liner system contains a geomembrane, then the cover sys-
tem should contain a geomembrane to prevent the "bath-
tub" effect. Likewise, if the bottom liner system is a nat-
ural soil liner, then the cover system barrier should be hy-
draulically equivalent to or less permeable than the bottom
liner system. A geomembrane used in the cover will pre-
vent the infiltration of moisture to the waste below and
may contribute to the collection of waste decomposition
gases, therefore necessitating a gas collection layer.
There are at least two options to consider under a liq-
uids management strategy, mummification and recircula-
tion. In the mummification approach the cover system is
designed, constructed, and maintained to prevent moisture
infiltration to the waste below. The waste will eventually
approach and remain in a state of "mummification" un-
til the cover system is breached and moisture enters the
landfill. A continual maintenance program is necessary to
maintain the cover system in a state of good repair so that
the waste does not decompose to generate leachate and
gas.
The recirculation concept results in the rapid physical,
chemical, and biological stabilization of the waste. To ac-
complish this, a moisture balance is maintained within the
landfill that will accelerate these stabilization processes.
This approach requires geomembranes in both the bottom
and top control systems to prevent leachate from getting
out and excess moisture from getting in. In addition, the
system needs a leachate collection and removal system
on the bottom and a leachate injection system on the top,
maintenance of this system for a number of years (depend-
ing on the size of the facility), and a gas collection system
223
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to remove the waste decomposition gases. In a modern
landfill facility, all of these elements, except the leachate
injection system, would probably be available. The bene-
fit of this approach is that, after stabilization, the facility
should not require further maintenance. A more impor-
tant advantage is that the decomposed and stabilized waste
may be removed and used like compost, the plastics and
metals could be recycled, and the site used again. If prop-
erly planned and operated in this manner, fewer landfill
cells could serve much of a community's waste manage-
ment needs for many years.
CONSTRUCTION QUALITY CONTROL AND
QUALITY ASSURANCE
Field data studies have clearly indicated that with the
development of a Construction Quality Assurance/Con-
struction Quality Control (CQA/CQC) program that the
performance of the waste management facility will
improve over a facility constructed without a good
CQA/CQC program.
CQA consists of a series of planned observations and
tests required to insure that the final product (the waste
management facility) will meet the project specifications.
CQA is a management tool and the plans, specifications,
observations, and tests are all used to provide a quantita-
tive means of acceptance of the final product. CQC con-
sists of a series of actions which provide a continuing
means of measuring and controlling the characteristic's of
the product in order to meet the specifications of the fin-
ished product. CQC is the production tool that is employed
by the manufacturer of materials and contractor installing
the materials at the site.
TECHNICAL GUIDANCE DOCUMENTS
The U.S. Environmental Protection Agency, in support
of hazardous and nonhazardous waste management fa-
cilities, developed three types of documents. The intent
of these documents was to assist designers of facilities
and reviewers of permits for these facilities. One docu-
ment, the permit guidance manual, addresses the type of
information required for a permit. The other two docu-
ments, the Technical Resource Documents and the Tech-
nical Guidance Document, contain information useful to
designers.
The Technical Resource Documents present summaries
of state-of-the-art technologies and evaluation techniques
determined by the Agency to constitute good engineering
designs, practices, and procedures. They describe current
technologies and methods for waste facilities, or for eval-
uating the performance of a facility design. Although em-
phasis is given to hazardous waste facilities, the informa-
tion presented in these TRDs may be used for designing
and operating nonhazardous waste treatment, storage and
disposal facilities.
The Technical Guidance Documents present design
and operating parameters or design evaluation techniques
that, if followed, would demonstrate compliance with the
United States regulations. This paper has presented the
current cover and liner regulations for hazardous waste
(Subtitle "C") and non-hazardous (Subtitle "D").
In addition to the documents described above the
Agency presents detailed seminars throughout the U. S.
Seminar publications, developed from these seminars, pro-
vide additional information useful to designers, operators
and owners of waste management facilities. A listing of
currently available documents is provided in the reference
section.
SUMMARY
Management of hazardous and nonhazardous wastes
will require the development of liner and cover systems
that will minimize the release of potential pollutants to the
environment. These systems, as designed and constructed
in the United States, will contain mixtures of geosynthetics
and natural soil materials. These designs have been gen-
erally described.
To insure that the facilities are constructed as designed,
the development of a CQA/CQC plan is recommended.
Specific objectives as well as key elements of the plan
have been provided.
Finally, the technical knowledge, presented through a
series of documents and publications have been identified.
REFERENCES
U.S. EPA, "Design, Construction and Maintenance of Cover Sys-
tems for Hazardous Waste, An Engineering Guidance Document," L'.S
Armv Ensineer Waterways Experiment Station, Vicksburg, MS, Ma\
1987, KTlS P8 87-191656.
L'.S. EPA, "Evaluating Cover Systems for Solid and Hazardou
Waste," Office of Solid Waste and Emergency Response Washington
D.C., SW 867, September 1982, NT1S PB 87-154894.
U.S. EPA, "Construction Quality Assurance for Hazardous Wast;
Land Disposal Facilities," Office of Solid Waste and Emergency Re-
sponse, Washington, D.C, EPA/53Q-SW-86-031, OSWER Policy Direc
live No. 9472,003, NTIS PB 87-132825.
U.S. EPA, "Design, Construction, and Evaluation of Clay Liner
for Waste Management Facilities," Technical Resource Document, Ha?
ardous Waste Engineering Research Laboratory, Office of Research an
Development, U. S. Environmental Protection Agency, Cincinnati, Of
EPA/530-SW-86-007F, September 1988, NTIS PB 86-184496.
U.S. EPA. "Lining of Waste Containment and Other Impoundmc
Facilities," Technical Resource Document, EPA-600/2-8S-052, Septerr
ber 19S8, NTIS PB 129670,
Moore, Charles A., "Landfill and Surface Impoundment Perfe
mance Evaluation," U.S. EPA SW-869. 1982. NTIS PB 81-166357,
Richardson and Koemer, "Geosynthetic Design Guidance for Ha
ardous Waste Landfill Cells and Surface Impoundments," EPA-600,
87-097, December 1987. NTIS PB 88-131263.
U.S. EPA, "Guide to Technical Resources for the Design of Lar
224
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Disposal Facilities," Risk Reduction Engineering Laboratory and Center
for Environmental Research Information, EPA/625/6-88/Q18, Cincin-
nati. OH. 1988.
U.S. EPA, "Seminar Publication; Requirements for Hazardous
Waste Landfill Design, Construction and Closure," Center for Environ-
mental Research Information, EPA/625/4-89/002, Cincinnati, OH, 1989.
U.S. EPA, 'Technical Guidance Document; Final Covers on Haz-
ardous Waste Landfills and Surface Impoundments," Office of Research
and Development. EPA/53O-SW-89-047, Cincinnati, OH, July 1989,
NT1S-PB89-233480.
U.S. EPA, "Technical Resource Document; Design, Construction
and Operation of Hazardous and Nonhazardous Waste Surface Im-
poundments," Office of Research and Development, EPA/530/SW-
91/054. Cincinnati, OH. June 1991. NTIS-PB91-204354.
U.S. EPA, "Technical Guidance Document; Inspection Techniques
for the Fabrication of Gcomembrane Field Seams," Office of Research
and Development, EPA/530/SW. 91/051, Cincinnati, OH, May 1991.
NTIS-PB92-109057
U.S. EPA. "Seminar Publication; Design. Construction of RCRA/
CERCLA Final Covers," Center for Environmental Research Informa-
tion, EPA/623/4-91/025. Cincinnati, OH, May 1991.
U.S. EPA, "Technical Ouidance Document; Construction Quality
Management for Remedial Action and Remedial Design Waste Con-
tainment Systems," Office of Research and Development and Office
of Solid Waste and Emergency Response, EPA/34Q/R-92/073. NT1S-
PB93-105625,
U.S. EPA. "Technical Guidance Document; Quality Assurance and
Quality Control for Waste Containment Facilities," Office of Research
ar.d Development and Office of Solid Waste and Emergency Response,
EPA/530/SW-93/
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completingj
—
1. REPORT NO. 2.
EPA/600/A-94/246
3. RECIPI
4. TITLE AND SUBTITLE
Review of Liner and Cap Regulations for Landfills
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert E. Landreth 513/569-7871
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
RREL/WMDDRD/MSWRMB
26 W. Martin Luther King Drive
Cincinnati, OH 45268
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Risk Reduction Engineering Laboratory--Cinti, OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
13. TYPE OF REPORT AND PERIOD COVERED
Published Paper
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Robert E. Landreth (513)569-7871. 16th National Waste Processing Conference,
June 6-8, 1994, Boston, MA. ; page 221-225
16. ABSTRACT
The U.S. Environmental Protection Agency through its research and field experiences
has developed control strategies for hazardous and municipal solid waste landfills and
surface impoundments. These control strategies include liner and cover systems. The
liner systems include double liners for hazardous waste and a single composite liner
for municipal solid waste. The.purpose of each individual component will be
discussed with options for using natural in-situ materials or geosynthetics. Although
natural soils are used as various components, emphasis has been placed on the use of
geosynthetics, including geomembranes, geonets, geotextiles, and plastic pipes. Cover
systems for both hazardous and municipal waste facilities are based on a multi-layer
design. The multi-layer component characteristics, including performance, thickness
and material type will be discussed. These designs include both natural soils and
geosynthetics.
It has been demonstrated with field data that the development of construction quality
control/quality assurance will improve the performance of the disposal facility.
Current programs and techniques used in the United States will be discussed.
17 KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATi Field/Group
Liner/Cap Regulation Waste
Landfill Solid Waste
Construction QA/QC Surface
Disposal Facility Impoundment
Design geosynthetics
State-of-the-art Technology Geonets
Field data Geotextles
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report!
Unclassified
21. NO. OF PAGES
7
20. SECURITY CLASS (This page;
Unclassified
22. PRICE
EPA Form 2220-1 (R.v. 4-77) previous edition is obsolete
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