EPA/530-SW-85-014
DRAFT
Minimum Technology Guidance
on
Double Liner Systems
for
Landfills and Surface Impoundments--
Design, Construction, and Operation
Protection
V_f — • • "~ J
00 - j Second version
^30 South Dearborn Street
Chicago, Illinois 60604 MaY 24,1985
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II
Minimum Technology Guidance on
Double Liner Systems for
Landfills and Surface Impoundments
TABLE .OF CONTENTS
PAGE
INTRODUCTION ---------------_______ m
FML/COMPOSITE DOUBLE LINER SYSTEM ---------- - l
I. Primary Leachate Collection and Removal Systems - - - 4
for Landfills
A. Guidance -------------------- 4
B. Discussion ------------------- 5
II. Double Liner Specifications ------------- n
A. Guidance -------------------- n
B. Discussion ------------------- 26
III. Secondary Leachate Collection Systems Between - - - 43
the Liners
A. Guidance -------------------- 43
B. Discussion ------------------- 45
IV. Construction Quality Assurance ----------- 50
A. Guidance -------------------- 50
B. Discussion ------------------- 52
FML/LOW PERMEABILITY SOIL DOUBLE LINER SYSTEM ------ 56
References ------------------------ 53
Suggested Reading List ------------------71
U.S. Environmental Protection Agency
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Ill
Introduction
On November 8, 1984, the President signed into law the Hazardous and
Solid Waste Amendments of 1984 (H5WA). Under Sections 3004(o) and 3015 of
the HSWA certain landfills and surface impoundments are required to have
"two or more liners and a leachate collection system above (in the case of a
landfill) and between such liners," unless the conditions for a statutory
variance are met. Section 3004(o)(5)(B) allows the use of a particular
type of liner design pending the issuance of EPA regulations or guidance
documents (through the notice and cement process) inplementing the double
liner requirement in Section 3004(o). This guidance document is intended to
provide guidance on designs in addition to the design set out in Section
3004(o)(5)(B) that the Agency believes meet the requirements of §§3004(o)
and 3015 of the HSWA. and are protective of human health and the environment.
This document identifies tvro such double liner systems.
The first double liner system includes a top liner and a composite bottom
liner (Figures 1 & 2). The top liner is designed, operated, and constructed
of materials to prevent the migration of any hazardous constituents into
such liner during the period the facility remains in operation (including a
30-year post-closure monitoring period). The top liner is a flexible membrane
liner (FML), which is addressed in this guidance in some detail. The bottom
liner consists of two components that are intended to function as one system,
hence, the term "conposite" liner. Like the top liner, the upper component
of the bottom liner is designed, operated, and constructed to prevent the
migration of any constituent into this component during the period of facility
operation, including the post-closure monitoring period. The upper conponent
of the composite liner is also a flexible membrane liner (EML). The lower
conponent of the bottom liner is designed, operated, and constructed to
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FIGURE 1
SCHEMATIC OF AN FML/COMPOSITE DOUBLE LINER SYSTEM
FOR A LANDFILL
Protective
Soil or Cover
(optional)
Primary Leachate
Collection and
Removal System
Secondary Leachate
Collection and
Removal System
Top Liner
(FML»
Bottom Composite
Liner
vovS o '^ ° ° ° ' ° 'Oiv? O . Q o:
OC. Solid Waste 2* ft-
"
i M i n M 1 1 M 1 1 1 ii ii 1 1 1
_S
(^Drainage Material
^Drainage Material
Low Permeability Soil
Native Soil Foundation
Upper Component
(FML)
Lower Component
(compacted soil)
(Not to Scale)
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FIGURE 2
SCHEMATIC OF AN FML/COMPOSITE DOUBLE LINER SYSTEM
FOR A SURFACE IMPOUNDMENT
Protective
Soil or Cover
(optional)
Secondary Leachate
Collection and
Removal System
Top Liner
(FML)
Low Permeability Soil
Native Soil Foundation
Bottom Composite
Liner
;;j;:::' Upper Component
(FML)
Lower Component
(compacted soil)
Note: Primary leachate collection system not used in surface impoundment.
(Not to Scale)
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VI
minimize the migration of any constituent through the upper conponent if a
breach in the upper conponent were to occur prior to the end of facility
operation, including the post-closure monitoring period. The lower conponent
of the composite bottom liner is a conpacted soil that should meet tecnivLcal
requirements set forth in this document.
The second design includes the performance standard from Section 3004(o)(5)(B)
This double liner system includes a top liner designed, constructed, and
operated of materials to prevent the migration of any constituent into such
liner during the period the facility remains in operation (including a 30-year
post-closure monitoring period), and a lower liner designed, operated, and
constructed to prevent the migration of any constituent through the liner
during this period (Figures 3 & 4). The top liner in this design is an FML
and the bottom liner is a conpacted low permeability soil. Section 3004(o)(5)(B)
provides that a three-foot tluck liner of recompacted clay or other natural
material will satisfy the lower liner requirement. Because EPA believes
that three feet of clay or other natural material will not prevent migration
in most cases, this document provides guidance on what the Agency believes
is an adequate lower liner. The Agency interprets the term "natural material"
to mean any naturally occurring soil that can be compacted, without man made
additives, into a liner with a permeability of 1 X 10~7cm/sec or less.
Although both of these double liner system designs are acceptable, this
guidance contains more information en the first design than the second. The
second design is more dependent on site specific characteristics, such as the
amount of annual rainfall, than the first design. Also, the second design
requires a series of assumptions on leakage rates, flow characteristics, and
other factors. Therefore, the specificity of guidance that is given en the
second double liner system design is more limited.
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FIGURE 3
SCHEMATIC OF AN FML/COMPACTEO SOIL DOUBLE LINER SYSTEM
FOR A LANDFILL
Protective
Soil or Cover
(optional)
Top Liner
(FMU
Drainage Material O"**~ <*»***
Primary Leachate
Collection and
Removal System
Secondary Leachate
Collection and
Removal System
Thick Layer *
Low Permeability Soil
Native Soil Foundation
Bottom Liner
(compacted soil)
« Thickness to be determined by break through time.
(Not to Scale)
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Protective
Soil or Cover
(optional)
Secondary Leachage
Collection and
Removal System
FIGURE 4
SCHEMATIC OF AN FML/COMPACTED SOIL DOUBLE LINER SYSTEM
FOR A SURFACE IMPOUNDMENT
Top Liner
(FML)
Thick Layer *
Low Permeability Soil
Native Soil Foundation
Bottom Liner
(compacted soil)
•Thickness to be determined by breakthrough time.
Note: Primary leachate collection system not used
in surface impoundment.
(Not to Scale)
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LX
The double liner system set out in Section 3004(o)(5)(B) and the two
double liner systems discussed in this guidance are not the oily double
liner systems that may be used to comply with the minimum technology requirements
of HSWA. Other double liner systems, depending on their design, operation,
location, and waste types to be received, may be acceptable. Alternative
double liner systems may include other amended soil materials with man made
products or natural materials such as soil cement, lime/soil mixture, or fly
ash/soil mixture. However, an owner/opera tor choosing to install an alternative
double liner system should confer with the Agency during the design and
construction of the system in order for EPA to ascertain whether the system
will meet the minimum technology requirements of HSWA.
For example, an owner/operator of an interim status landfill or surface
impoundment who wants to install one of the two double liner systems described
in this guidance below the ground-water table should request review of the
design plans prior to construction. Liner and leachate collection system
installation below the ground-water table involves many site-specific
considerations. Such systems are not specifically discussed in this guidance.
Owners and operators choosing the design in §3004(o) (5) (3) or one of the two
designs that are discussed in this guidance (particularly the FML/composite
design) should be able to proceed with construction with substantially less
Agency interaction. (This is likely to be the case for both interim status
and permitted units.)
This guidance is intended to incorporate the current state-of-the-art
regarding the design, construction, and operation of hazardous waste land
disposal units. The attempt has been made to include an element of practicality
in specifying how to construct a unit. However, this guidance does not address
all components of facility design, construction, operation, and closure. Por
example, it does not address the final cover requirements for landfills and
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X
certain surface impoundments, nor does it discuss considerations for freeboard
in inpoundment design and operation. The Agency's previously issued guidance
(July 1982) continues to be applicable in these areas. [NOTE: EPA does
not believe §§264.228(a)(2)(iii)(E) or 264.310(a)(5) for permitted units
require the installation of two EMLs in the final cover when two EMLs are
used in the double liner system. A single FML in the final cover that is
equivalent to the thicker FML used in the double liner system will be
considered to have an equivalent permeability. ]
This guidance is one step in the Agency's efforts to imp lenient the
mininum technology requirements of §§3004(o) and 3015 of the HSWA. We expect
to formalize many of these guidelines in the future by incorporating them
into the Agency's regulations.
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FML/COMPOSITE DOUBLE LINER SYSTEM
The FML/conposite double liner system consists, at a mininum, of a
primary leachate collection and removal system (for landfills), a top FML
liner, a secondary leachate collection system, and a bottom composite FML/low
permeability soil liner. A detailed cross section of the basic conponents
of the FML/conposite double liner system for landfill and surface impoundment
units is shown in Figure 5. The function of the primary leachate collection
and removal system at landfills is to minimize the head (depth) of leachate
on the top liner during operation and to remove liquids through the post-closure
monitoring period. The leachate collection and removal system should be
capable of maintaining a leachate head of less than 1-foot. The top liner
should be designed, constructed, operated, and maintained to prevent migration
of waste liquid constituents during operation (including the post-closure
monitoring period) and should allow no more than de minimis infiltration of
any constituent into the liner itself. The secondary leachate collection
system between the two liners should be designed, constructed, operated,
monitored, and maintained to rapidly detect, cc^lect, and remove liquids
entering the collection system for treatment through the post-closure monitoring
period. The bottom liner consists of tv*o components that are intended to
function as one system, hence, the term "composite" liner. Like the top
liner, the upper conponent of the bottom liner should be designed, operated,
and constructed to prevent the migration of any constituent of the waste
liquid into the upper component during the period of facility operation,
including the post-closure monitoring period. For design purposes, the
post-closure monitoring period should nominally be assumed to be 30 years.
The lower component of the bottom liner should be designed, operated, and
constructed to minimize the migration of any constituent of the waste liquid
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Materials
FIGURES
SCHEMATIC PROFILE OF AN FML/COMPOSITE
DOUBLE LINER SYSTEM FOR A LANDFILL
Dimensions and Specifications
Nomenclature
Graded Granular Filter Medium
Granular Drain Material
(bedding)
Flexible Membrane Liner (FML)
Granular Drain Material
(bedding)
Flexible Membrane Liner (FML)
Low Permeability Soil, Compacted in Lifts
(soil liner material)
Note: FML thickness > 45 mils
recommended if liner is not
covered within 3 months.
A •
% °K v.-
''''
Recommended Thickness > 6 in.
Maximum Head on Top Liner = 12 in.
Recommended Thickness 2* 12 in.
Hydraulic Conductivity > IxlO'2 cm/sec
V—Recommended Thickness of FML >30 mils
(see note)
Recommened Thickness > 12 in.
Hydraulic Conductivity > IxlO"2 cm/sec
Drain Pipe —
- Recommended Thickness of FML > 30 mils
(see note)
Recommended Thickness > 36 in.
Recommended Hydraulic Conductivity < IxlO'7
cm/sec
Prepared in 6 in. Lifts
Surface Scarified Between Lifts
Unsaturated Zone
Groundwater Level
Saturated Zone
W////////////M
Sol id Waste
Filter Medium
Primary Leachate Collection and
Removal System
Top Liner (FML)
Secondary Leachate Collection and
Removal System
Compression Connection (contact)
Between Soil and FML
Bottom Liner (composite FML and
compacted low permeability soil)
Native Soil Foundation/Subbase
po
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through the upper component if a breach in the upper component were to occur
prior to the end of facility operation, including the post-closure monitoring
period. Compacted low permeability soil is reconirended for the lower conponent.
EPA believes that this design is effective in protecting human health and the
environment because the combination of the twD components in the bottom liner
system provides for virtually complete removal of waste or leachate by the
leachate collection system if a leak were to occur in the top liner.
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I. Primary Leachate Collection and Renoval Systems for Landfills
Contents
Page
A. Guidance ----- __________ _ 4
Objective 4
Design specifications ------------- 4
Construction specifications - 5
Operation specifications 6
B. Discussion
A. Guidance
Overall Design, Construction, and Operation Objective
The primary leachate collection and removal system system should be
designed to ensure that the leachate depth above the top liner does not
exceed one foot; be constructed of materials that can withstand the chemical
attack that results from waste liquids or leachates; be designed and constructed
so as to withstand the stresses and disturbance from overlying wastes,
waste cover materials, and equipment operation; be designed and operated to
function without clogging through the post-closure monitoring period; and be
operated to collect and remove leachate through the post-closure monitoring
period. Components should be properly installed to assure that the specified
performance of the leachate collection system is achieved.
Design
The primary leachate collection and removal system should have:
(a) At least a 30 centimeter (12 inch) thick granular drainage layer
that is chemically resistant to the waste and leachate, with a hydraulic
conductivity not less than 1 x 10~2 cm/sec and with a minimum bottom slope
of 2 percent.
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Innovative leachate collection systems incorporating synthetic drainage
layers or nets may be used if they are shown to be equivalent to or more
effective than the granular design, including chemical compatibility,
flow under load, and protection of the FML (e.g., from puncture).
(b) A graded granular or synthetic fabric filter above the drainage
layer to prevent clogging. Criteria for graded granular filters and for
synthetic fabric filters are found in numerous publications such as the
Geotextile Engineering Manual available fron the Federal Highway Administration
and others. The granular drainage material should be washed to remove fines
before installat ion.
(c) A drainage system of appropriate pipe size and spacing on the bottom
of the unit to efficiently collect leachate. These pipe materials should be
chemically resistant to the waste and leachate. The piping system should be
strong enough to withstand the weight of the waste materials and vehicular
traffic placed on or operated on top of it.
(d) A primary leachate collection system that covers the bottom and
sidewalls of the unit.
(e) A sump in each unit or cell should be capable of automatic and
continuous functioning. The sump should contain a conveyance system for the
removal of leachate fron the unit such as either a sump pump and conveyance
pipe or gravity drains.
(f) A written construction quality assurance (CQA) plan prepared by the
owner/operator to be used during construction of the double liner system
including the primary leachate collection and removal system. See Section
IV, "Construction Quality Assurance", for specific details.
Construction
(a) The owner/operator should use the construction quality assurance
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plan to monitor and document the quality of materials used and the conditions
and manner of their placement during construction of the primary leachate
collection and removal system. See Section IV, "Construction Quality Assurance",
for specific details.
(b) The documentation for the CQA program should be kept on-site in the
facility operating record maintained for the landfill unit.
Operation
The following operational procedures should be followed:
(a) The leachate removal system should operate automatically whenever
leachate is present in the sump and should remove accumulated leachate at
the earliest practicable time to minimize the leachate head on the liner
(not to exceed 12 inches);
(b) Inspect weekly and after major storm events for proper functioning
of the leachate collection and removal system, and for the presence of leachate
in the removal sump. The owner or operator should keep records on the system
to provide sufficient information that the primary leachate collection system
is functional and operated properly. We recommend the amount of leachate
collected be recorded in the facility operating record for each unit on a
weekly basis?
(c) Cleaning out of collection lines periodically; and
(d) A storage permit for collected leachate, if required. Collected
leachate is subject to the prohibition on placement of liquids in landfills
in RCRA §3004(c).
B. Discussion
The Agency believes that practical designs for leachate collection and
removal systems can maintain a leachate depth of one foot or less, except
perhaps temporarily (for a few days) after major storms. The specifications
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presented here, judiciously applied, are expected to accomplish that requirement.
The minimum thickness (30 centimeters or 12 inches) of the drainage
layer allows sufficient cross sectional area for transport of drainage leachate.
The two-percent minimum slope is also intended to promote drainage. In most
cases, the Agency believes thicker drainage layers and greater slopes will
be selected by owners and operators to maximize the efficiency of the leachate
collection and removal system. The hydraulic conductivity of not less than
1 X 10~2 on/sec was chosen because materials widely used as drainage media
are coarse enough tiiat their hydraulic conductivities are estimated to be
1 X 10~2 cm/sec or greater.
It is not clear if the statutory requirements of §3004(o)(l)(A)(i) require
the primary leachate collection system to be on the sidewalls of a landfill.
The current Part 264 requirements in §264.301(2) require a collection and
removal system immediately above the liner to collect and remove leachate.
The previous liner guidance dated July, 1982, did not specify whether the
leachate collection system was only to cover the bottom or also the sidewalls
of the unit. The Permit Writer's Guidance Mani-ul for Hazardous Waste Land
Treatment, Storage, and Disposal Facilities, October 1983, indicates that
the need for a leachate collection system of the sidewalls of a landfill
should be based on site-specific conditions of expected leachate flow over
the life of the facility. Generally, we feiuourage the installation of a
primary leachate collection system on both the base and sidewalls of double
liner systems under §3004(o)(1)(A)(i). The two designs in this guidance
recommend leachate collection on the sidewalls because it allows leachate to
drain to the sump faster and minimize ponding of leachate within the waste
on the sidewalls of the top liner.
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The following is a list of factors that affect liquid transmission in
the leachate collection system drain layer:
0 Inpingenent rate of liquid on the collection drain layer;
0 Slope of the drain layer;
0 Diameter and spacing between the drainage pipes;
8 Coefficient of hydraulic conductivity of the saturated sand or
gravel drain layer; and
0 Cleanliness (lack of fines) of the sand or gravel.
A method for estimating quantity of liquids collected and liquid depth above
the liner is presented in Landfill and Surface Impoundment Performance Evaluation,
SW-869, April 1983 (EPA 83).
Drain pipe diameter and spacing are ittportant because they affect the
head that builds up on the top liner between pipes. The closer the pipes
are together, the less the head. Also, the pipe diameter should be large
enough to efficiently carry off the collected leachate. Since the philosophy
for all aspects of liner design is to minimize liquid transmission through
the liner system, the head on the liner should be miaunized. But the spacing
and size of the drainage piping system necessary to acconplish this depends
on other characteristics of the drainage layer (e.g., hydraulic conductivity)
and on the inpingement rate of liquids, which is a function of precipitation
and the effectiveness of the cover system. The Agency is, therefore, not
specifying minimum spacing or pipe diameter in this guidance. However, EPA
believes that designs incorporating 6-inch diameter perforated or slotted
pipes spaced 50 to 200 feet (15 to 60 meters) apart will effectively minimize
head on the liner system in most cases. Information on leachate collection
is presented in Appendix V of Lining of Waste Impoundment and Disposal Facilities,
SW-870, March 1983 (EPA 83A). The owner or operator should demonstrate
through appropriate design calculations that the maxinum recommended one-foot
head will not be exceeded.
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The leachate collecticn and removal system should be overlain by a
graded granular filter or synthetic fabric filter. The purpose of tliis is
to prevent clogging of the voids in the drain layer by infiltration of fines
from the waste. If a granular filter is used, it is inportant that the
relationship of grain sizes of the filter medium and the drainage layer be
appropriate if the filter is to fulfill its function to prevent clogging of
the drainage layer and not contribute to clogging. Criteria for graded
granular filters and for synthetic fabric filters are found in numerous
sources such as:
Graded granular filters:
- Earth Manual. 1984. Bureau of Reclamation, U.S. Department of the
Interior. Government Printing Office, Washington, DC.
Geotextiles:
- Koerner, Robert M., and J.P. Welsh. 1980. Construction and Geotechnical
Engineering Using Synthetic Fabrics. John Wiley and Sons, New York.
- Horz, R.C. 1984. Geotextiles for Drainage and Erosion Control at
Hazardous Waste Landfills. EPA Interagency Agreement No. AD-96-F-1-400-L.
U.S. EPA, Cincinnati, Ohio.
- Geotextile Engineering Manual, Training \anual, Federal Highway Administratio
Innovative leachate collection systems that are equivalent to, or more
effective than, the granular system described above may be used. These
innovative systems such as plastic nets can be very thin, on the order of
one-inch thick, and have the drainage capacity of a sand layer one-foot
thick. These systems should be capable of maintaining a leachate head of one
foot or less. The following criteria should be addressed for determining
equivalence:
0 Design - hydraulic transmissivity (i.e., the amount of liquid that
can be removed)
- compressibility (i.e., ability to withstand expected overburden
pressures while remaining functional)
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10
- conpatibility (chemical) with waste liquid
- conpatibility (mechanical) with the EML (i.e., will not
deform the EML under the expected overburden)
- slope stability
0 Construction - Construction characteristics (i.e., ease of construction)
0 Operation/performance characteristics
- drainage or flow characteristics (i.e. how fast liquids will
flow and what volume will flow)
- tine required to return the leachate head to one foot or less
after a rainfall event
- material creep
- useful life of system
- ability to resist clogging
- ability to verify performance.
An owner or operator wishing to use a leachate collection system other than
the recommended one should compare the properties of his design against the
recatmended design using the above criteria. If equivalent, or better he
should proceed; if not, he should abandon the alternate design. If one or
nore of the factors is not equivalent, the collection system will probably
not perform well, and will potentially become a source of constant trouble
to its owner/operator.
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11
II. Double Liner Specifications
Contents
Page
A. Guidance 11
Objective 11
Design 12
a. EML top liner ________ — 12
b. Gonposite bottom liner 17
Construction _ 19 -
a. FML 19
b. Low permeability soil ______ 20
Operation ___ 26
B. Discussion ______ 26
A. Guidance
Overall Design, Construction, and Operation Objective
All new surface impoundments and landfills, new units, lateral expansions,
and replacement units must have two liners. The two liners nust be designed,
constructed, and operated to protect human heal'-h and the environment. The
top liner should be designed, operated, and constructed of materials to
prevent the migration of any waste liquid constituents into such liner during
the period the unit remains in operation (including any post-closure monitoring
period), and should allow no more than de minimis infiltration of waste
constituents into the liner itself. The top liner discussed herein is a
flexible membrane liner (FML). The secondary leachate collection system is
between the two liners. The bottom liner consists of tvro components that
are intended to function as one system, hence, the term "composite" liner.
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Like the top liner, the upper component of the bottom liner should be designed,
constructed, and operated to prevent the migration of any constituents into
this conponent during the period of facility operation, including any post-closure
monitoring period. The upper compcnent of the bottom liner of this design
is also an EML. The lower conponent of the bottom liner should be designed,
constructed, and operated to minimize the migration of any constituent through
the upper conponent if a breach in the upper conponent were to occur prior
to the end of unit operation, including the post-closure monitoring period.
The lower conponent of the bottom liner is a conpacted low permeability soil
material. All liner materials should be resistant to the waste liquid
constituents the liner will encounter, and be of sufficient strength and
thickness to withstand the forces it will encounter during construction and
operation. Foundation preparation is recontnended to ensure that the structural
stability of the subgrade is sufficient to support the liners without damaging
them and to prevent failure due to pressure gradients (including mechanical,
gas, and liquid static and external hydrogeologic forces). The double liner
system should cover all areas likely to be exposed to waste and leachate.
Design
0 This liner system should be constructed conpletely above the seasonal
high water table (i.e., in unsaturated soil).
0 The two liners should consist of the following, as a minirtum:
(a) An FML top liner;
(1) The EML top liner should be at least a 30 mils thick; however, if
the liner is to be exposed to the weather for an extended period before it
is covered by a protective soil layer or the waste, or if the liner is to be
operated without a protective cover, it should be at least 45 mils in thickness.
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13
Many units will require a thicker liner to prevent failure while the unit is
operating, including any post-closure monitoring period. The adequacy of
the selected thickness should be demonstrated by an evaluation considering
the type of FML material and site-specific factors such as: expected operating
period of the landfill or surface impoundment unit, pressure gradients,
physical contact with the waste and leachate, climatic conditions (environmental
factors), the stress of installation, and the stress of daily operation
(e.g., placing wastes in the landfill or sludge removal in surface impoundments),
Stresses tend to be higher for surface impoundment units than for landfill
units. Several factors can increase liner stresses in surface impoundments
such as: (1) cleaning or maintenance activities; (2) thermal stress; (3)
hydrostatic pressure (head and wave action); (4) abrasion; (5) weather exposure
(ultraviolet light, oxygen, ozone, heat, and wind); and (6) operating conditions
(inlet and outlet flow, active life, exposure to animals, treatment processes).
Because of these factors, uncovered surface impoundments generally require
thicker liners than the 45-mil minimum. Thicknesses of 60-100 mils have been
necessary in some applications. A protective l~yer covering the liner in
surface impoundments can reduce the stresses on the liner. The Agency will
consider appropriate historical data and actual test data regarding the
performance of liner materials of the designed thickness as part of the
evaluation of the permit application.
(2) Liners should be chemically resistant to the waste and leachate
managed at the unit. The Agency strongly prefers test data because the
demonstration of chemical resistance should be based on representative waste
effects. The EPA Test Method 9090 (October 1, 1984, proposal or revised
editions) or an Aqercy approved equivalent test method should be used to
test chemical resistance of liners. Complete copies of the text of sampling
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14
and analytical methodologies addressed in the October 1, 1984, proposed
rules (including nethod 9090) are available from the National Technical
Information Service (NTIS), 5285 Port.Royal Road, Springfield, Virginia
22161, (703) 487-4650. The document number is PB-85-103-026. In judging
chemical compatibility of wastes and membranes, the Agency will consider
appropriate historical data or actual test data if obtained under longer or
more severe test conditions.
(3) The National Sanitation Foundation (NSF) presents liner material
properties and factory seam requirements in their Standard Number 54 for
Flexible Membrane Liners, November 1983. The Agency suggests that material
and seam specifications such as those in the National Sanitation Foundation
standard be used to assure material quality from the liner manufacturer.
Liner materials listed by the National Sanitation Foundation for industrial
service, or liner materials that are not listed but consistently meet the
specifications of the NSF Standard 54, are acceptable for assuring quality
from the manufacturer. Test methods used to establish these requirements
should comply with applicable American Society of Testing and Materials
(ASTM) procedures, recommended methods in EPA document SW-870 Lining of
Waste Impoundment and Disposal Facilities (tables VIII-1 to 7) (EPA 1983A),
or an equivalent method when available. The FMLs covered by NSF standard
54 include at least the following:
0 Polyvinyl Chloride (PVC)
0 Polyvinyl Chloride Oil Resistant (PVC-OR)
8 Chlorinated Polyethylene (CPE)
0 Butyl Rubber (IIR)
0 Polychloroprene (CR)
0 High Density Polyethylene (HOPE)
0 Ethylene-Propylene Diene Terpolymer (EPDM)
0 Epichlorohydrin Polymers (CD)
0 Polyethylene Ethylene Propylene Alloy (PE-EP-A)
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15
High Density Polyethylene Elastomeric Alloy (HDPE-A)
Chlorosulfonated Polyethylene (CSPE)
Chlorosulfonated Polyethylene, Low Vfeter Absorption (CSPE-LW)
Thermoplastic Nitrile - PVC (TN-PVC)
Thermoplastic EPDM (T-EPDM)
Ethylene Interpolymer AlJoy (EIA)
Chlorinated Polyethylene Alloy (CPE-A)
The address for the National Sanitation Foundation is:
3475 Plymouth Road
P.O. Box 1468
Ann Arbor, Michigan 48106 USA
(4) ETMLs should be free of pinholes, blisters, holes, and contaminants,
which include, but are not limited to, wood, paper, metal, and nondispersed
ingredients.
(5) The compounding ingredients used in producing FMLs should be first
quality, virgin materials providing durable and effective formulations for
liner applications. Clean rework materials containing encapsulated scrim or
other fibrous materials should not be used in the manufacture of flexible
membrane liners (FML) used for hazardous waste containment. Clean rework
materials of the same virgin ingredients generated from the manufacturer's
own production may be used by the same manufacturer, provided that the finished
products meet the material specification requirements.
(6) EMLs in landfill units, and in units with the minimum recommended
thickness, should be protected from damage from above and below the membrane
by a least 30 centimeters (12 inches) nominal, 25 centimeters (10 inches)
minimum, bedding material (no coarser than Unified Soil Classification System
(USCS) sand (SP) with 100 percent of the washed, rounded sand passing the
1/4 inch sieve) that is free of rock, fractured stone, debris, cobbles,
rubbish, and roots, unless it is known that the FML material is not physically
impaired by the material under load. The surface of a completed substrate
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should be properly compacted, smooth, uniform, and free from sudden changes
in grade. The secondary leachate collection system or the low permeability
soil may serve as bedding materials when in direct contact with EMLs if they
meet the requirements specified herein. Polymeric materials such as geotextiles
and synthetic drainage layers may also serve as bedding materials when in
direct contact with either surface of the top IML or with the upper surface
of the FML component of the bottom liner, if they provide equivalent protection.
In determining equivalent protection given by geotextile or other specific
materials, the Agency will consider historical data and actual test data
that relate to site-specific conditions. To demonstrate that a synthetic
drainage layer can serve as bedding material, it should be shown that the
synthetic drainage layer does not exhibit brittle failure under overburden
stresses and stresses caused by equipment used for construction or waste
placement.
Note: In most cases an FML should not be in contact with native, in situ soil.
Note: Light geotextile bedding material may require an additional
precaution if the slopes are exposed to high velocity winds.
'(7) For surface impoundment and landfill units in which the sidewalls
will be uncovered and exposed for extended periods before wastes are placed,
the design of the bedding material used below the top liner should be highly
permeable and include gas venting if the potential for gas generation under
the bottom liner exists, or if the slopes of a surface impoundment will be
exposed to high velocity winds.
(8) Penetration of a liner by any designed means should be avoided.
Where structures are necessary, such as:
0 Pipes (both horizontal and vertical),
0 Vertical support columns,
0 Inlets, outlets,
0 Sumps, and
0 Divider walls,
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it is essential to obtain a secure, liquid-tight seal between the structure
and the FML. An FML nay be attached to a structure with a mechanical-type
seal supplemented by chemically conpatible caulking, adhesives, or heat
fusion to effect a liquid-tight seal. Conpaction of areas adjacent to the
structure should be to the same density as the surrounding soil to minimize
differential settlement. Sharp edges on the structure should not come in
contact with an FML.
(9) Bridging or stressed conditions in the FML should be avoided with
proper slack allowances for shrinkage of the FML during installation and
before the placement of a protective soil layer or waste.
(b) A composite bottom liner;
(1) The composite bottom liner consists of two ccnpcnents, an upper FML
component and a lower corrponent of conpacted low permeability soil.
(2) The upper FML component should be of at least a 30-mil membrane;
some units will require a thicker liner to meet the site conditions without
probable failure during construction and while the unit is operating, including
any post-closure monitoring period. The adequacy of the selected thickness
should be demonstrated by an assessment of the type of liner material and
site-specific factors. The liner should be chemically resistant to the
waste and leachate managed at the unit. The EPA test method 9090 or an
equivalent test method should be used to test chemical resistance of liners.
In judging chemical compatibility of the membrane with the waste to be managed,
the Agency will consider appropriate historical data and actual test data
obtained under longer or more severe test conditions.
(3) The upper FML component of the conposite bottom liner should be protected
from damage from above by at least 30 centimeters (12 inches) of bedding
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material no coarser than Unified Soil Classification System (USGS) sand (SP)
that is free of rock, fractured stone, debris, cobbles, rubbish, and roots,
unless it is known that the liner material under load is not physically
inpaired by the material. The subgrade to the synthetic upper conponent
will be the uppermost lift of the conpacted lower conponent. This lift
should be sufficiently snoothed to provide a good bed for the overlying
synthetic material. The secondary leachate detection, collection, and renoval
system serves as the top bedding material and the low-permeable soil conponent
of the bottom liner serves as the lower bedding material and should meet the
requirements specified herein. Polymeric materials such as geotextiles nay
also be used as top bedding materials when in direct contact with the liner
if they provide equivalent protection. They should not be used as the bedding
below the FML, as they would increase the transmit sity between the two conponents
of the bottom liner. In determining equivalent protection for geotextile,
the Agency will consider historical data and actual test data that relates
to site-specific conditions.
(4) The FML upper conponent and the soil lower conpcnent interface trust
be in direct contact, and be designed and constructed to provide a compression
connection (contact) between the two coriponents to minimize flow between them.
The two components are maintained in contact by the overburden load. The design
and construction should minimize void space, channels, and other conditions
promoting lateral flow of liquids at this interface. This requirement is
not intended to preclude liner installers from purposely leaving designed
folds in the synthetic liner material. No fabric or other high-permeability
bedding material should be used between the upper and lower conponents that
would have high transmissivity. Overburden pressure exerted on the secondary
liner from overlying materials may be sufficient to adequately reduce the
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potential for lateral flow. EPA recognizes that there may be procedures or
materials which would further reduce the transmissivity of this interfacial
zone and encourages demonstrations to- that effect.
(5) The soil conpcnent of the conposite liner should be at least 90
centimeters (36 inches) of cottpacted, enp laced, low permeability soil with an
in-place saturated hydraulic conductivity of 1 X 10~^ cm/sec or less.
The compacted material must be free of rock, fractured stone, debris, cobbles,
rubbish, and roots that would increase hydraulic conductivity or serve to
promote preferential leachate flow paths.
(6) The foundation subsoil that underlies the compacted low permeability
soil component should be structurally irmobile during construction and operation
of the unit (including any post-closure monitoring period).
(c) The owner/operator should prepare a written construction quality
assurance plan to be used during construction of the double liner system,
including both the FML top liner and the composite bottom liner. See Section
IV on Construction Quality Assurance for specific recofrmendations.
Construction
0 The earth substrates and base materials should be maintained in a
smooth, uniform, and compacted condition during installation of each liner
and components.
0 Surface impoundment and landfill units should be constructed with liners
that meet the following, as a minimum:
(a) EML liners:
(1) The liner should be installed (seamed) at ambient temperatures within
the range specified by the manufacturer of the particular liner. Temperature
extremes may have an effect on transportation, storage, field handling and
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placement, seaming, and backfilling (where required).
(2) When the field seaming of the FML is adversely affected by moisture,
portable protective structures and/or'other methods should be
used to maintain a dry sealing surface.
(3) Liner installation should be suspended when wind conditions may
adversely affect the ability of the installers to maintain alignment of
seams and integrity of membranes and seams.
(4) Field seaming of FMLs should be performed when weather conditions
are favorable. The contact surfaces of the FML should be free of dirt,
dust, and moisture including films resulting from condensation in weather
conditions of high humidity. Seams should be made and bonded in accordance
with the supplier's recormended procedures. Both destructive and nondestructive
testing methods should be used to evaluate seam integrity. All on-site
seams should be inspected by nondestructive testing techniques to verify
their integrity. Periodic samples should be removed from both factory and
field seams and tested for seam integrity by destructive tests (tension and
peel tests). On-site nondestructive seam samples should be made and evaluated
with identical liner material, adhesive, and technique prior to actual field
seaming each day, or when conditions change. Seam testing methods are described
in more detail in an upcoming EPA report, Construction Quality Assurance for
Land Disposal Facilities.
(5) Proper equipment should be selected in placing bedding material
over FMLs to avoid undue stress.
(b) Low permeability soil:
(1) EPA is conducting studies to evaluate the construction criteria
that most significantly influence the hydraulic conductivity of compacted
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low permeability soil liners. Until specific research and/or demonstration
data are available, the following are suggested as the best available procedures
for optimizing construction of the compacted bottom conponent of the conposite
liner:
(i) Remove all lenses, cracks, channels, root holes, or other structural
nonuniformities that can1 increase the nominal in-place saturated hydraulic
conductivity of the liner above 1 X 10~^ cm/sec.
(ii) Construct the liner in lifts not exceeding 15 centimeters (6 inches)
after compaction to maximize the effectiveness of compaction throughout the
lift thickness. Each lift should be properly interfaced by scarification
between lifts.
(iii) Scarify sufficiently between each lift so as not to create a zone
of higher horizontal hydraulic conductivity at the interface of the lifts.
(iv) Break up clods and homogenize the liner material before compaction
of each lift using mixing devices such as pug mills or rotary tillers. All
oversized materials (such as trash, large roots, wood, or large clods) should
be removed in order to facilitate moisture control operations, maximize
compaction, reduce heterogenity, and minimize overall hydraulic conductivity
of the compacted liner.
(v) Thoroughly mix in moisture needed to bring the liner to the desired
water content using mixing devices such as pug mills, rotary tillers, or
other effective methods.
(vi) Compact the liner after allowing a sufficient time for added water
to penetrate to the center of the clods while not allowing so rruch time
after water addition that the exterior of the larger clods becomes drier
than optimum. The larger clods should be field checked for moisture distribution.
(vii) Take the necessary precautions to assure that the desired moisture
content is maintained in the compacted liner to avoid desiccation cracking.
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Precautions that are effective at preventing desiccation cracking should be
taken both between the placement of lifts and after conpletion of the liner.
(viii) Construction should not take place using frozen or other indurated
soil, and precautions should be taken to assure that the liner is not allowed
to freeze after placement.
(ix) Sidewalls should be constructed so as to minimize flow between the
lifts. EPA believes this can best be acooitplished with lifts that are laid
down parallel to the slope.
(x) A demonstration should be made that sidewalls can be effectively
compacted at the maximum slope to be used in the design. The Agency suggests
a maximum slope of 3 horizontal to 1 vertical.
(xi) Consideration should be made of the vector of compactive effort
when calculating the number of passes necessary to obtain a certain degree
of compaction on sidewalls.
(xii) The uppermost lift should be scraped and steel rolled to produce a
smooth surface prior to placement of the EML upper component. This procedure
is intended to minimize lateral flow between components of the composite
bottom liner.
(2) EPA recommends that a representative test fill be constructed using
the soil, equipment, and procedures to be used in construction of the compacted
low permeability soil component to the composite liner in the full scale
facility. The test fill should be used to verify that the specified density/
moisture ccntent/hydraulic conductivity values can be consistently achieved
in the full scale facility. Test fills have been used to validate both
design and construction procedures for critical earthen structures around
dams and nuclear power plants. In order for the data collected from the
test fill to be useful, however, construction control of the test fill must
be strict and well documented.
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Previously-developed data that describes the performance of an installed
liner can be used, provided documentation is available on all the factors
discussed above. EPA is not, however'aware of any facility that currently
has this data on loand.
All information gathered during construction and subsequent testing of
the test fill should be documented. The CQft. program to be followed during
ccnstruction of the full scale facility should be strictly followed during
construction of the test fill (Corps of Engineers, 1977). Recommended mininum
test fill ccnstruction details are as follows:
(i) Construction using the same compactable materials, compaction equipment,
and exact procedures as will be used to construct the full scale facility
liner. All applicable parts of the quality assurance plan should be precisely
followed to monitor and document construction of the test fill.
(ii) The test fill should be constructed at least four times wider than the
widest piece of equipment to be used in construction of the full scale facility.
(iii) The test fill should be long enough to allow construction equipment
to reach normal operating speed before enterino the area to be used for testing
(see Figure 6).
(iv) Construction so as to facilitate the use of field hydraulic conductivity
tests and/or a complete quantification of all underdrainage. Field hydraulic
conductivity tests should be conducted on the compacted test fill material as
a verification of results of laboratory tests conducted on undisturbed samples
taken frcm the compacted test fill material. The field hydraulic conductivity
tests need only verify that the hydraulic conductivity is 1 X 10~7 on/sec or
less, not its actual value. These undisturbed samples can then be used for
compacted liner/leachate compatibility testing.
(v) Construction so as to determine the relationship of the following to
the moisture ccntent/density/hydraulic conductivity values obtained in the
field:
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Figure 6
AT LEAST THREE SIX-INCH THICK LIFTS OF COMPACTED SOIL
A DRAINAGE LAYER OR UNDERDRAlNAGE COLLECTION SYSTEM
UJ
a.
2:I SLOPE
L« DISTANCE REQUIRED FOR CONSTRUCTION EQUIPMENT TO REACH NORMAL
RUNNING SPEED
W DISTANCE AT LEAST FOUR TIMES WIDER THAN THE WIDEST PIECE OF
CONSTRUCTtOM EQUIPMENT
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0 Compaction method (detailed specifications of the caipaction equipment);
0 Number of passes of the compaction equipment;
0 Mixing method (and resulting raxinum clod size);
0 Conpaction equipment speed; and
0 Unconpacted and compacted lift'thickness.
(vi) A set of index properties should be selected that will be used to
monitor and document the quality of construction obtained in the test fill.
These index properties should include at least the following:
0 Hydraulic conductivity (undisturbed samples);
0 In-place density and water content;
0 Maximum clod size;
0 Particle size distribution; and
0 Atterberg limits.
Data from these tests shall be used as standards for comparison with values
obtained on samples from the full scale liner to indicate inplace field
hydraulic conductivity.
(3) All lifts of the compacted low permeability soil liner that are
part of the 3-ft minimum thickness should have a in-place hydraulic conductivity
of 1X10"7 cm/sec or less. This hydraulic conductivity value should be
verified both in the test fill liner and by the comparison of index property
values between the test fill and each lift in tlie full scale liner. The
values obtained should be numerous enough to fully document the degree of
variability of all the index properties in both the test fill and each lift
in the full scale liner.
(c) The owner/operator should implement a written quality assurance
plan for monitoring and documenting the quality of liner materials used and
the conditions and manner of their placement during construction of the top
FML and composite bottom liners. See Section IV on "Construction Quality
Assurance" for specific recommendations.
(d) The documentation for the CQA program for construction of the double
liner should be kept on-site in the facility operating record.
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Operation
The following operational criteria apply:
(a) The top (FML) liner should prevent migration of waste constituents
into the liner through the closure period, except for de minimis leakage.
(b) The placement of removable coupons of the EML above the top liner
is a technique for providing waste/liner chemical compatibility information
during the operating period. Coupons are samples of the FML's used in the
construction of the tvo liners that are placed in contact with wastes or
leachate in the landfill or surface impoundment. The coupons are tested
after various exposure periods in the unit to determine how the properties
of the liner change over the operating period. This information, when compared
to short-term compatibility data, can provide an early warning that the
liner is degrading faster than anticipated and allow for corrective measures
by the owner. The Agency reccnmends that landfill and surface impoundment
owners consider removable coupon testing if wastes are likely to vary somewhat
during operation.
(c) The owner should have en-site guideline? for operation and maintenance
of the double liner system, which include recommendations on such subjects
as:
- Frequency and documentation of inspection,
- Testing and repair of liner,
- Animal and plant control,
- Erosion control,
- Unacceptable practices,
- Placement of waste, and
- Coupon test schedule (optional).
B. Discussion
The EPA believes that an FML used in this double liner system, whether
the top liner or the upper component of a composite liner, should meet the
following criteria:
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- A minimum thickness depending on the service;
0 For buried FMLs the mininum thickness should be 30 mils when the
membrane will be covered within three months by a protective layer
against mechanical and weather conditions.
0 For membranes that will be buried, but left unprotected for periods
greater than 3 months, the mininum thickness should be 45 mils.
0 For all liners used in impoundments that are left uncovered and
exposed to the weather and experience light work on the surface,
the minimum thickness should be 45 mils.
0 The thickness of scrim layer, geotextile backing, or "other reinforcing
material should not be used in computing a minimum, recommendation.
0 For many units, particularly surface impoundments with exposed surfaces,
FML's of 60-100 mils may be required to meet the mechanical stress
requirements.
0 The stresses on exposed liners are generally greater for surface
impoundments because of exposure to more severe environmental conditions
(climate), loading and unloading during daily operation, and sludge removal.
Because of the more severe operation conditions, surface impoundments
require substantially thicker liners. A protective layer covering the
liner can reduce the stresses on the liner.
- Sufficient strength to prevent failure due to pressure gradients
(including static head and external hydrologic forces, stresses of
installation, and the stresses of daily operation);
- Compatibility with the waste to be managed in the unit;
- Low permeability; and
- Capable of being seamed to produce high strength, liquid-tight seams
that retain their integrity during liner installation and on exposure
to wastes for the duration of the operating life of the unit, including
the postclosure monitoring period.
One of tlie primary reasons for failure of synthetic liners is damage
(i.e., punctures, rips, and tears). Damage occurs during installation and/or
during operation. The owner operator needs to demonstrate that the selected
FML thickness is adequate for the site-specific conditions the liner will
encounter while the unit is in operation (including any post-closure monitoring
period).
EPA believes thickness and strength of the liner material are major
factors in maximizing serviceability and durability. However, the lack of
current technical data relating liner thickness for specific material types
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to successes and failures of liner systems prevents more specific guidance
on thickness. The following is a list (EPA, 1983) of potential failure
modes that should be considered in selecting the FML polynver type and thickness
to maximize liner serviceability and durability:
Physical Modes of Failure
Abrasion
Creep
Differential settling
Hydrostatic pressure
Puncture
Stress-cracking (partly chemical)
Tear stress
Thermal stress
Chemical Modes of Failure
Extraction of plasticizer and soluble ingredients
High pH>10
Hydrolysis
Attack by ionic species
Low pH<2
Ozone-cracking
Attack by solvents and organic chemical species
Ultraviolent light attack
Biological Modes of Failure
Microbial attack (of plasticizers in FML compounds)
Liner failure mechanisms are addressed in a U.S. EPA Technical Resource
Document, Lining of Waste Impoundment and Disposal Facilities, SW-870,
March 1983. This document describes and discusses the categories and charac-
teristics of liner failure in a service environment. The document is available
from the U.S. Government Printing Office, publication number S/N 055-000-00231-2,
$11.00, Superintendent of Documents, Washington, D.C. 20460. Kays (1977)
also provides detailed discussion on liner failure mechanisms and methods to
avoid failures for cut-and-fill reservoirs.
EPA believes that, for design purposes, the post-closure monitoring
period can rominally be assumed to be 30 years. The double liner system.
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should be designed so that no leakage out of the unit is expected through
the operating period, including the 30-year post-closure monitoring period.
To help guard FMLs against damage, such as punctures, tears, and rips
due to contact with sharp objects or other conditions, it is good practice to
protect them from above and below by a minimum of 12 inches of bedding material.
In landfills, the act of placing wastes sometimes causes damage (e.g., due to
dropping of wastes or driving of vehicles on the liner); also, over extended
time periods the wastes themselves may be capable of causing damage to the
top FML and to the leachate drainage and collection system because they contain
sharp objects or abrasives.
For landfill units, a leachate drainage and collection system nust be
placed above the top liner. This layer can be made of materials that meet
both bedding and drainage material requirements. However, EPA suggests
that for these units an additional layer of bedding material be installed
above the top filter layer as well as below the top FML, unless it is known
that the FML is not physically impaired by the materials, including pipes in
the secondary leachate collection system. The Jrain pipes in both collection
systems should be adequately protected against damage caused by waste placement
and/or equipment operating on the working surface.
Bedding layers should consist of materials that are no coarser than
sand (SP) as defined by the Uniform Soil Classification System (USCS). Use
of a sand layer is corrmon practice for protection of membranes and pipes
from damage due to contact with grading equipment and materials, sharp materials
in the soil, etc. As discussed above, the bedding layer need not be a separate
layer, as the materials in the secondary leachate detection, collection, and
removal system will often meet the necessary criteria.
For surface impoundments, a bedding layer above an FML also protects the
FML from damage due to exposure to sunlight and wind while the unit is in
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operation. However, the bedding material is not always necessary above the
top liner, since direct contact with the liquid wastes does not represent
the same potential for puncture that is present in landfills. Nevertheless,
the liner can be damaged during sludge removal or other dredging operations.
Where mechanical equipment is used, EPA recommends a minimum of 45 centimeters
(18 inches) of protective soil or the equivalent covering the top liner,
unless it is known that the EML will not be damaged by the sludge removal
practices. Some EML materials are known to be degraded by ultraviolet radiation
and must be covered. Also, wind can get under the edge of exposed EMLs,
causing flapping and whipping, which can lead to tears. These problems have
occurred most commonly above the liquid level near the edge of the FML. As
a result, it is common practice to cover FMLs with 6 to 12 inches of earthen
material to prevent degradation due to sunlight and hold the liner down.
The edges of BMLs are usually secured by anchor trenches at their perimeter.
Of course, if the design is such that wind creates no difficulties, and if
it is known that tiie FML is not subject to solar degradation, then these
precautions are not necessary. The addition of a cover over the EML is
expected to extend the service life of the liner. The bedding material need
not be a separate layer, as the secondary leachate detection, collection,
and removal system materials will often meet the necessary criteria for
bedding.
Chemical testing of all construction material components is prudent
because liners can be degraded by certain chemical species that may be present
in the waste. Because wastes and liner chemical characteristics are almost
infinitely variable, it is difficult to generalize concerning incompatibility
or compatibility. The Agency, therefore, strongly suggests (and prefers)
test data as the appropriate way to demonstrate the compatibility of the
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waste to be managed and the liner naterials under consideration. Test results
should demcnstrate the acceptability of the selected liner materials. New
test data may not be needed for units-that have a well defined waste conposition
and for which previous test data showing that the proposed liner chemical
characteristics are very predictable.
Waste liner material compatibility tests should be conducted using
representative sanples of wastes and leachates to which the liner is to be
exposed. Several methods for obtaining sanples of hazardous waste are discussed
in Section one of Test Methods for Evaluating Solid Waste (SW-846).
An acceptable test method for assessing the compatibility of waste
liquids and EML's is the "Immersion Test of Membrane Liner Materials for
Chemical Compatibility with Wastes," found in EPA's Method 9090. In this
test, samples of the candidate EML's are ijrmersed at two temperatures in
sanples of the waste liquid to be managed and exposed for four months.
After exposure for one-month intervals, an FML sample is tested for important
strength characteristics (tensile, tear, and puncture) and weight loss or
gain. The Agency considers any significant deterioration in any of the
measured properties to be evidence of incompatibility unless a convincing
demonstration can be made that the deterioration exhibited will not impair
the liner integrity over the life of the facility. Even though the tests
may show the amount of deterioration to be relatively small, the Agency is
concerned about the cumulative effects of exposure over very much longer
periods than those actually tested.
At present, no standard test method is available for assessing the
compatibility of specific low permeability soils with a given waste liquid.
Nevertheless, the compatibility of a soil with a waste liquid has been measured
by comparing the permeability of the soil to water and to the waste liquid.
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The Agency incorporated the National Sanitation Foundation's (NSF)
standard specifications for flexible membrane liners into this guidance to
provide suggested minimums values for'physical properties. An NSF committee
has been studying the subject for some time, and EPA believes that the
specifications developed are reasonable and well thought out. Compliance
with the NSF standard attests only to the basic quality of the liner itself
and not to the advisability of its application under any given set of waste
and unit-specific circumstances.
The top liner, an FML, is required to prevent migration of constituents
of the waste liquid into the liner during the period the unit remains in
operation (including any post-closure monitoring period) except for de minimis
leakage. EPA recognizes that membranes will not always have zero leakage
and that de minimis leakage may occur. De minimis leakage can occur as a
result of vapor passing through the liner, very small imperfections in the
liner that occur very rarely, or a seam that has a very small crack or hole.
Although FML's are nonporous-honogeneous materials, vapor diffusion can transmit
water and other liquids with dissolved constituents through synthetic liners.
The transmission involves (1) sorption of the constituents of the waste
liquid into the membrane, (2) diffusion through the FML, and (3) evaporation
or dissolution of the constituents on the downstream side of the membrane.
The principal driving force for permeation through an FML is the gradient
across the liner in concentration, chemical potential, or vapor pressure of
the individual constituents in the liquid or vapor. Permeability of an
individual permeant depends upon its solubility and diffusion characteristics
in a specific liner. De minimis leakage can also occur because of small and
infrequent breaches in the liner that were not detectable during construction
with current practical state-of-the-art construction quality assurance programs.
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Detected leakage tray be clue to Leakage through either the top or bettor;
liner.
EPA believes that current state-Qf-the-art technology for FML installation
allows for hazardous waste management units to be built that will have very
low leakage rates at installation. EPA does not have a specific maximum de
minimis leakage rate that can be recommended. However, based on currently
available preliminary field data, laboratory test results, and professional
judgment, EPA believes that de minimis leakage should be approximately
1 gal]on/acre/day or less. This rate should not be taken as a hard and fast
rule because there are conditions where vapor transmission potentially
could exceed this value. Also, this value does not apply to organic liquids,
many of which can permeate an FML independently of the water in waste liquid.
Some organic constituents can transmit at considerably higher rates than
water, if the organic constituents are soluble in the membrane and organic
concentration en the downstream side of the membrane is essentially zero.
Dr. H. August et al, (1984), has shown laboratory permeation rates for
concentrated hydrocarbons on 1 mm thick HOPE FML's were between 1 and SOg/rt^/day
varying with the waste chemical structure and its affinity to the HDPE.
Another finding of this study was that very dilute hydrocarbon solutions
sometimes give high permeation rates of the hydrocarbons because of the
relatively high solubility of the hydrocarbons cortpared to water in the
HDPE. The concentration of organic waste in the liner surface can be higher by-
several orders of magnitude than the adjacent leachate or liquid waste containing
hydrocarbons. Current laboratory tests cannot be related directly to estiinate
field rates of permeation because the tests do not simulate the ability ©f
soil under the liner to transport the waste away from the liner. (See the
suggested reading material list for additional information.) Review of
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infonration from recently constructed double synthetically lined surface
inpoundments shows that current state-of-the-art technology for installing
synthetic liners is close to achieving 100% containment efficiency. The
liner installations studied had extensive construction quality control to
assure the seams did not leak.
A conposite secondary liner including both FML and compacted soil
conponents was selected as a result of various studies and analyses conducted
by the Agency. A conposite liner has several advantages. The FML component
inproves the efficiency of the secondary leachate collection system that
must be installed between the top and bottom liners (see Section III). Any
improvement in the collection efficiency of this system would allow earlier
detection of liquids between the liners. Capillary forces present in an unsaturated
low permeability soil liner may cause the initial leakage through the top
liner to be absorbed before it is detected. FMLs on the other hand, can
achieve virtually complete rejection of liquids and are, thus, more effective
than compacted soils at detecting small amounts of leachate and overall
removal efficiency. For this reason, a FML was= selected for the upper conponent
of the bottom liner.
While less efficient at detecting initial top liner leakage, compacted
low permeability soil liners are not subject to the same types of installation
and operational problems as FMLs. A problem that causes a puncture in a
FML probably will not form a hole all the way through a compacted soil liner.
In addition, a compacted soil liner has a potential to both minimize leakage
through the FML and attenuate certain constituents in the leachate in the
event of a leak. In the event of leakage through the FML component of the
composite liner, the low hydraulic conductivity (1X10~7 cm/sec or less) in
the compacted soil liner would have the effect of both decreasing this leakage
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35
and increasing efficiency of the secondary leachate collection system. For
these reasons, a conpacted low permeability soil liner was selected as the
lower component of the corrposite bottom liner. The conpacted soil is a low
permeability soil that has been compacted in 6-in. lifts, with an inplace
hydraulic conductivity of 1 X 10~^ cm/sec or less. For purposes of this draft
guidance, "compacted soil" is not meant to include materials such as soil cement,
lime soil mixtures, or fly ash soil mixtures, and other soil amendments including
natural or man made.
Objectives of the conpacted low permeability soil component of the
composite bottom liner include the following:
(1) to serve as a protective bedding material for the FML upper component;
(2) to serve as a long term structurally stable base for all overlying
materials;
(3) to attenuate constituents in liquids that might leak through the
FML upper component; and
j
(4) to minimize the rate of leakage through breaches in the
FML upper component.
Objective number one can be met if the compacted soil is smoothed prior
to the placement of the FML upper component. In most cases, three feet of
compacted low permeability soil will be adequate to meet objective number two.
However, the adequacy of a given conpacted thickness will depend on the soil
being conpacted, the degree of compaction, the total expected load, and the
geologic and hydrologic setting. Documentation should be provided that
describes the capability for a given thickness to both serve as adequate
bedding and provide sufficient structural support.
Objective three, attenuation of constituents, can best be met by as-suring
that the conpacted soil is as homogeneous as possible. Preventing the formation
of cracks (by preventing desiccation or freezing of the liner during or
after placement) and reducing the number of large pores (by reducing clod
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36
size and optimizing conpactive procedures) are two ways to enhance the atten-
tuative capacity of the soil liner. If leachate has only relatively small
pores through which to migrate, the waste constituents come in closer contact
with the adsorptive surfaces of the conpacted materials. One way to document
the attenuative capacity of a given thickness of conpacted soil is through
the use of breakthrough curves (Griffen, 1978 and Anderson, 1982). To closely
simulate actual field conditions, these breakthrough curves should be determined
on undisturbed samples of the conpacted soil collected from the test fill.
Objective four can be achieved by minimizing both the potential for
lateral flow between the FML upper and compacted lower components of the
bottom liner and by minimizing the flux of liquid through the compacted
lower component. Lateral flow between the components of the bottom liner
can be minimized by obtaining a good contact between the compacted lower component
and the FML upper component. -This contact is obtained by a combination of
the following:
(1) smoothing the top of the uppermost lift of the conpacted soil by
use of smooth wheel steel rollers; and
•(2) application of overburden pressure to the top of the FML upper
component.
Overburden will be supplied by the weight of the overlying leachate collection
layer, and waste (in the case of surface impoundments) and by the leachate
collection layer, waste, and final cover (in the case of landfills). Additional
procedures and materials are encouraged that may further reduce the lateral
flow between the secondary liner components.
Minimizing the flux of liquid through the compacted soil can be accomplished
as follows:
(1) minimizing the hydraulic gradient under which leachate will move; and
(2) minimizing hydraulic conductivity of the compacted soil.
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There are two ways to minimize the hydraulic gradient: (1) reduce the depth
of standing liquids in the leachate collection systems; and (2) construct a
thicker compacted soil liner. Besides lowering the hydraulic gradient,
constructing a thicker compacted liner should reduce the probability that a
blemish of any kind would penetrate all the way through the compacted soil.
Whether referred to as blemishes, macrof eatures, or structural non-unifor-
mities, construction inperfections may increase the overall saturated hydraulic
conductivity by several orders of magnitude. Methods to reduce actual in-the-
field hydraulic conductivity of a conpacted soil should be included in the
construction inspection program to both prevent and detect these imperfections.
Details of the information that should be gathered before, during, and after
construction of a compacted soil (which should serve to reduce the number of
these inperfections) are given under "Construction Quality Assurance" (section IV),
Hydraulic conductivity testing on the in-place conpacted low permeability
soil is recommended because of concern that laboratory tests tend to under-
estimate the actual hydraulic conductivity in the field by a factor of 10 to
1000. The following recent references discuss the causes and magnitude of
differences between field-measured and laboratory-measured hydraulic conductivity:
0 Daniel, D. E:, 1984. Predicting Hydraulic Conductivity of Clay liners.
ASCE Journal of Geotechnical Engineering, 110(2):235-300.
0 Griffin, R. A. et al. 1984. Migration of Industrial Chemicals and
Soil-waste Interactions at Wilsonville, Illinois. In: Proceedings
of the Tenth Annual Research Symposium on Land Disposal of Hazardous
Waste (EPA 600/9-84-007) USEPA Municipal Environmental Research Laboratory,
Cincinnati, OH 45268.
0 Herzog, B. L. and W. J. Morse. 1984. A Comparison of Laboratory and
Field Determined Values of Hydraulic Conductivity at a Waste Disposal
Site. In: Proceedings of the Seventh Annual Madison Waste Conference.
University of Wisconsin-Extension, Madison, Wisconsin, p. 30-52.
0 Boutwell, G.P. and V.R. Donald, 1982. Conpacted Clay Liners for Industrial
Waste Disposal, Presented ASCE National Meeting Las Vegas, April 26,
1982.
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One reason why higher hydraulic conductivities are often obtained with
field tests is that sanples used in laboratory tests can be more readily
prepared without the defects that can .greatly affect actual hydraulic conductivity.
Methods that are used to prepare soil liners in the field are difficult to
sinulate in the laboratory. One exanple is the method of compaction. Soil
liners are often corrpacted in the field with a kneading action through the
use of sheepsfoot rollers. In contrast, soil liner sanples are usually
prepared in the laboratory using impact conpaction. Even though "identical
densities may be obtained with different methods of compaction, the soil
samples conpacted by different metliods may have very different hydraulic
conductivities (Mitchell, 1976).
There are a variety of other reasons for the large discrepancies reported
between laboratory and field tests. Samples prepared in a laboratory are
not subject to the climatic variables (such as cracking due to either freezing
or desiccation) (EPA 1984A). There may also be a tendency to run laboratory
tests on samples of selected finer textured soil materials (Olson and Daniel
1981). It is often suggested, however, that the most important reason for
observed differences is that field tests can evaluate nuch larger and, hence,
more representative'samples than is practical in laboratory tests.
EPA believes that field hydraulic conductivity tests are essential to
verify the requirement to have an in-place hydraulic conductivity of 1X10~7
cm/sec or less. Currently available field hydraulic conductivity tests, if
conducted on the actual compacted soil liner may, however, cause substantial
delays in construction and result in other problems due to prolonged exposure
of the liner. In addition, it would be extremely costly if it were determined
from field tests on the actual liner that it did not meet or exceed performance
standards. Much time and effort can be saved if, prior to construction of
the actual liner, a test section of the liner is prepared and tested. These
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39
tests can be used to document the capability of the proposed materials and
construction procedures that result in a ccrpacted soil liner that meets the
desired performance standards. Therefore, the EPA recommends that a test
fill be constructed using the same borrow soil, compaction equipment, and
construction procedures as proposed for the full scale facility. The test
fill is also recommended for use in demonstrating the actual in-place hydraulic
conductivity of the compacted soil liner.
Field hydraulic conductivity tests of the compacted soil in the test fill
are necessary to assure that the materials and procedures used in the field
will result in a compacted soil liner with a hydraulic conductivity of IXICT^
on/sec or lower. Field testing is not intended to preclude the use of laboratory
testing in the design or construction phase or as a means of evaluating
liner-leachate compatibility. It is expected that the overall design and
construction quality assurance (OQA) program will include a mixture of both
field and laboratory hydraulic conductivity tests.
As appropriate methods are developed and verified, the EPA intends to
require field hydraulic conductivity tests be conducted on the full scale
facility. Field hydraulic conductivity tests can be performed in the test
fill without causing delays during construction of the full scale facility.
The field test used should be capable of verifying that the hydraulic conductivity
of the compacted soil liner is 1X10~^ cm/sec or less.
Field infiltrometers capable of measuring very low hydraulic conductivities
in compacted soil liners have been developed and reported by Anderson et al
(1984), Day (1984), and Day et al (1985). An alternative to the use of field
infiltrometers is the use of a system for capturing and collecting all under-
drainage from the test fill. Day (1984) used such an underdrain to evaluate
the accuracy of results obtained from field infiltrometers. While the field
infiltrometers were found to accurately measure hydraulic conductivity, the
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underdrain was considered aven More accurate.
Both infiltration and underdrainage tests should be conducted until
stable flew and/or drainage rates are obtained. Where infiltrometers are
used, there should be enough replicate tests to document areal variability
in the hydraulic conductivity of the liner to the test fill. A sufficient
number of index property tests (listed earlier in this section) should be
conducted to acconplish the following:
(1) verification of the aspects of the CQA plan related to compacted
soil liners; and
(2) document the degree of variability in each of the properties tested
in the compacted soil liner for both the test fill and full scale facility
In addition to being used as a site for field hydraulic conductivity
tests, the test fill should be used to verify all elements of the design and
construction of the soil liner. These elements should include at least the
following:
(1) verification that the proposed soil material is uniformly suitable
to be compacted into a liner (i.e., no cobbles, sand lenses, or indurated
rraterials).
(2) verification that the equipment and procedures for breaking up
clods, mixing in water, and compactinc, the soil are suitable for
consistently achieving the required hydraulic conductivity specifi-
cation.
(3) verification that the CQA plan is sound in all respects. The proposed
CQA plan for construction of the full scale facility should be
followed exactly as applied to construction of the test fill. If
methods to improve the CQA plan are documented during construction
and testing of the test fill, these improvements should be incorporated
into the CQA program implemented during full scale facility construction.
Technical personnel who will be in charge of day to day implementation
of the CQA plan on the full scale facility should also monitor and thoroughly
document construction and testing of the test fill. This documentation
should include at least the following:
(1) a detailed description of the type of equipment used during the
borrow and construction operations,
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41
(2) location of work, including borrow and construction sites;
(3) size, location, number, and identification of test sanples collected
and results of all tests performed;
(4) a diary of all relevant climatic and working conditions that may
affect construction of the full scale liner;
(5) index of all tests and results that will be used to compare the
liner constructed in the test fill to the full scale liner; and
(6) test fill report that compiles all documentation on the construction
of the test fill and includes all raw data and test results.
Laboratory hydraulic conductivity tests should be conducted"on undisturbed
sanples collected from the soil liner in the test fill. Care should be
taken to avoid conditions that bias test results. Examples of these conditions
include excessive effective confining pressure (Boynton and Daniel, 1985;
Anderson, 1982) and sidewall flow (Daniel et al 1985). Methods for collecting
undisturbed samples of soil liners have been suggested by Anderson et al
(1984) and Day (1984). The undisturbed samples may not provide hydraulic
conductivity values that precisely reflect field values. However, comparison
of values obtained from the test fill and full scale liners should provide
an indicator of gross changes in either the materials or procedures used in
construction.
EPA believes that additional testing is warranted to evaluate the hydraulic
conductivity of landfill and surface impoundment sidewalls. Especially in
surface impoundments, the sidewalls may be the predominant pathway by which
leachate can migrate beyond the liner systems. At this time however, the
Agency is not aware of a suitable method for evaluating hydraulic conductivity
of the sidewalls other than by construction of a costly scale impoundment.
There would need to be separate underdrains for the sidewalls and bottom
portions of the liner or it would be difficult to determine how much each
portion was contributing to the total underdrainage. EPA is temporarily
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deferring the recommendation for sidewall testing to allow interested parties
to develop economical and effective test methods. Comments are requested on
the follev/ing:
(1) Are tests of the hydraulic conductivity of landfill and surface
impoundment sidewalls necessary?
(2) Are there methods available for evaluating the hydraulic conductivity
of sidewalls?
(3) Are there additional methods that should be developed to facilitate
this testing?
In construction of FMLs, consideration should be given to the effects
from humidity in the air. Seaming of EMLs with some solvent cements at
high levels of relative humidity can result in moisture condensation on the
adhesive surface during the seaming process and may result in poor adhesion.
A relative humidity requirement may not be necessary for seaming techniques
that rely on heat to bond the liner sheets, as the heat could prevent moisture
from condensing on warm surfaces of the FML.
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III. Secondary Leachate Collection System Between The Liners
Contents
Page
A. Guidance ------_-__-------------- 43
Objective 43
Design --------------------- — - 43
Construction --------------------- 45
Operation ----------------------- 45
B. Discussion 46
A. Guidance
Overall Design, Construction and Operation Objective
The system should be capable of rapidly detecting, collecting, and removing
liquid entering the collection system; be constructed of materials that can
withstand the chemical attack that results from wastes or leachates, and the
stresses and disturbances from overlying wastes, waste cover materials, and
equipment operation; be designed and operated to function without clogging;
and be operated to detect, collect, and remove liquid through the post-closure
care period. This guidance also sets out methods for proper installation
of components to assure that the specified performance of the leachate collection
system is achieved.
Design
The secondary leachate collection system should have:
(a) A drainage layer that will permit rapid detection, collection, and
removal of any migration of liquid into the space between the liners. The
drainage layer should also be designed to collect and remove liquids rapidly
and to produce little or no head of liquid on the bottom liner.
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(b) Materials that are chemically resistant to the waste and leachate,
a minimum bottom slope of 2 percent, and a minimum hydraulic conductivity of
1X10"2 cm/sec.
(c) A system of drainage pipes of appropriate size and spacing on the
bottom of the unit to efficiently remove leachate.
An innovative leachate collection system such as a synthetic drainage
layer will be considered by the Agency if it can be demonstrated to be equivalent
to a conventional granular system with pipes and meets (a) and (b). These
materials must be chemically resistant to the waste and leachate; they must
be compatible with and non detrimental to the FML and not collapse under the
designed load.
(d) Direct contact with the FML component of the bottom liner.
(e) A sump of appropriate size to efficiently collect leachate and be
positioned at least 30 centimeters (12 inches) below the drainage layer
grade. Each landfill or surface impoundment unit should have its own sump.
For landfills, the sump for the secondary leachate collection system must be
separate from the primary leachate collection s>imp.
(f) A collection system that cover all areas between the double liners
likely to be exposed to waste and leachate.
(g) Methods of measuring and recording fluid volumes in the collection
system sump.
(h) The owner/operator should implement a written construction quality
assurance plan during construction of the double liner system, including the
secondary leachate collection system. See Section IV on Construction Quality
Assurance for specific details.
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Construction
(a) The owner or operator should use the construction quality assurance
plan to monitor and document the quality of materials used and the conditions
and manner of their placement during construction of the collection system
of the unit.
(b) The documentation of the CQA program should be kept on-site in the
facility operating record,
(c) The secondary collection system, including sump, should be free of
liquids and hazardous constituents when the waste management unit begins
operation.
Operation
The following operational measures should be followed;
(a) Removal of liquids, if any, on a daily basis, minimizing the head on
the ccnposite liner;
(b) The owner or operator should establish an inspection schedule that
will allow him to determine that the system is functional and operated properly.
EPA recommends that the removal sump be inspected for the presence of liquids
and proper operation of the system on each operating day or, at a miniiajm,
weekly during the active life depending upon site-specific conditions, and
at least quarterly during closure and post-closure. The owner or operator
should keep records on the system to provide sufficient information that the
secondary leachate collection system is functional and operated properly.
Documentation may include the amount of leachate present in the detection,
collection, and removal system of the unit. This information should be
recorded in the facility operating record;
(c) Repair of damaged leachate collection system corrponents as soon as
practicable during the operating period;
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(d) As a general matter EPA will include in draft permits a requirement
that the owner or operator notify the Regional Administrator, in writing,
of the presence of liquids in the secondary leachate collection system in a
timely manner. Such notification may include, if necessary:
(i) leakage rate (quantity);
(ii) the concentrations of hazardous constituents [indicator parameters specified
by 264.98(a)].
EPA may, on a case-by-case basis, consider requiring owners and operators
of permitted units to respond to leaks in the top liner, if this requirement
is necessary to protect human health and the environment.
(e) A storage permit for collected leachate, if required.
If the unit is not yet permitted (i.e., it is an interim status unit), the
owner/operator should modify the Part B application indicating the unit has
liquids in the secondary leachate collection system. The Agency will consider
this information at permitting to determine if the liner is leaking.
B. Discussion
The Agercy believes that it is practical t^ design and operate a secondary
leachate collection system to rapidly detect liquids in the space between the
liners, minimize the head on the bottom coitposite liner, and remove leachate
for treatment. The specifications presented here, judiciously applied, are
expected to accomplish these requirements.
The following is a list of factors that affect liquid transmission in
the drain layer of the leachate collection system:
0 Impingement rate of liquid on the collection drain layer;
0 Slope of the drain layer;
0 Size and spacing of the drainage pipe; and
0 Hydraulic conductivity of the saturated sand or gravel drain
layer.
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Drainage pipe diameter and spacing are inportant because they affect
the time to liquid detection, rate of removal, and the head that builds up
on the bottom composite liner between pipes. The pipe diameter should be
large enough to efficiently carry off the collected leachate rapidly. Since
the philosophy for all aspects of liner design is to minimize the transmission
of waste constituents through the liner system, the head on the bottom liner
should be minimized. The closer the pipes are together, the more quickly
liquids are likely to be detected. However, the spacing and size of the piping
system necessary to accomplish this depends on other characteristics of the
drain layer (e.g., hydraulic conductivity) and on the impingement rate of
liquids from the leak. Unlike the primary leachate collection system for
landfills and piles, the secondary leachate collection system detects liquids
as well as collecting and removing them. Thus, pipe size and spacing need
be sufficient for rapid transmission of liquids and need not be designed to
remove some predetermined volume rate of flow. EPA is, therefore, not specifying
minimum spacing or size in this guidance. Nevertheless, a reasonably sized
drainage system, coupled with an efficient sump system Jor removing collected
liquids, will result in the capacity to remove leaking liquids, except in
the case of severe breaches of the top liner.
Innovative secondary leachate collection systems that are equivalent to
or more efficient than conventional granular systems may be used. The following
criteria should be used to determine equivalence:
0 Design
- hydraulic transmissivity (i.e., the amount of liquid that can
be removed);
- compressibility (i.e., ability to withstand overburden pressure
while remaining functional);
- compatibility (mechanical) with the liners (i.e. thin, low-
modulus FML's in contact with some drainage materials may
distort under pressure);
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- ability to collect leachate;
- compatibility with leachate and waste;
0 Construction method
0 Operation/performance characteristics
- drainage or flow characteristics (i.e., how fast liquid will flow
and what volume will flow)
- sensitivity to leakage/small leaks;
- time required for detection of leachate;
- ability to verify performance ;
- reusability of the system once a leak is detected; and
- useful life of the system.
An owner/operator wishing to use an innovative collection system should
compare the properties of his design aqainst a conventional granular design
that uses the recommended design specification [see Design (a),(b) and (c)].
If the alternative drain layer is equivalent, he may proceed; if not, the
alternative design should be abandoned. If one or more of the factors are
not equivalent, the collection system would probably not perform as well as
a conventional granular system and would be a source of constant trouble to
its owner/operator.
If the owner or operator wishes to determine the source of liquids
found in the secondary collection system, the fallowing records on the design,
operation, and closure of landfill and surface impoundment units may provide
useful information:
0 Subsurface drilling logs including seasonal ground-water
elevations;
0 "As-built" drawings, certified by a professional engineer, for the
double liners and collection system(s);
0 Analytical data indicating the waste characteristics over time and
the leachability of these constituents under site-specific conditions
as included in the waste analysis plan;
° Accurate tables and plots of measured primary (for landfills) and
secondary leachate collection system fluid volumes;
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0 Tables and plots of monthly averages of data from primary and secondary
leachate analyses (consistent parameters should be used);
8 Construction quality assurance documentation report;
0 Other supporting data; e.g., rainfall, terrperature, etc.; and
0 An explanation prepared during design to explain why observed leachate
nay not be due to a leak in the top liner.
Additionally, EPA suggests that the owner/operator may determine that
simple statistical analyses (such as conparing the quality of liquids in the
leachate collection system to the quality in the leak detection system), may
be helpful in developing assessments of top liner integrity. The use of tracers
to determine the extent of migration could also be used.
The Agency believes that it is practical to operate a collection system
between two liners. Sites are currently using these systems to monitor the
performance of the top liner. The collection system allows the owner/operator
to detect, collect, and remove liquids in the secondary leachate collection
system.
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IV. Construction Quality Assurance
Contents
Page
A. Guidance -------------------------- 59
Objective 50
Design and Construction ----------------- 51
B. Discussion ------------------------- 52
A. Guidance
Overall Design, Construction, and Operation Objective
All new surface impoundments and landfills, new units, lateral expansions,
and replacement units nust have at least tvo liners with a leachate collection
system betaken the liners (and above for landfills). The double liners and
collection system(s) must be designed, constructed, and operated to protect
human health and the environment. To assure that a completed double-liner
system meets or exceeds all projected design criteria, plans, and specifications,
a construction quality assurance (CQA) program is necessary. In addition,
the regulations for permitted units (§§264.226 and 264.303) specifically
require liners to be inspected during construction for uniformity, damage,
and imperfections (e.g., holes, cracks, thin spots, or foreign materials);
immediately after construction EML's must be inspected to ensure tight seams
and joints, and the absence of tears, punctures, or blisters.
As part of the CQA program for compacted soil liners, a test fill should
be constructed using the same material procedures and equipment that will be
used in the full scale facility. The CQA plan to be followed during the
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full scale facility construction should be exactly followed during construction
of the test fill.
Design and Construction
(a) The owner/operator should sutnit and inplement a written construction
quality assurance plan to be used during construction of the primary leachate
collection system (for landfills), secondary leachate collection, and top
and composite bottom liners. The plan should be used in monitoring and
documenting the quality of materials used and the conditions and'manner of
their placement. The plan should be developed, administered, and documented
by a registered professional civil or geotechnical engineer with experience
in hazardous waste disposal facility construction and construction site
inspections. While the specific content of the construction quality assurance
plan will depend on site-specific factors, the following specific components
should be included, at a minimum:
0 Areas of responsibility and lines of authority in executing the CQA
plan;
0 Qualifications of GQA personnel;
0 Specific observations, and tests - preconstruction, construction, and
post-construction tests to verify that materials and equipment will
perform to specifications, and that the performance of the individual
parts of the double-liner system conform to design specifications.
As completed, the individual parts of the double-liner installation
should be tested for functional integrity. The FML joints, seams,
and mechanical seals should be checked both during and after installation.
A variety of testing methods can be used such as:
- hydrostatic
- vacuum
- ultrasonic
- air jet
- spark testing.
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In addition to hydraulic conductivity tests on undisturbed saitples
taken from the conpacted soil layer during construction, the low-permeable
soil layer should be tested for functional integrity through the use of
field hydraulic conductivity testing on the conpleted soil layer when
practical. The collection layer(s) should be tested to assure the
components are functioning as designed.
0 Sampling program design; the frequency and scale of observations and
tests, acceptance-rejection criteria, corrective measures, and statistical
evaluation.
0 Documentation of OQA should include daily recordkeeping (observation
and test data sheets, problem reporting and corrective measures data
sheets), block evaluation reports for large projects, design engineer
acceptance reports (for errors, inconsistencies, and other problems),
and final documentation. After completion of the double-liner system,
a final documentation report should be prepared. This report should
include summaries of all construction activities, observations, test
data sheets, problem reports and corrective measures data sheets,
deviations from design and material specifications, and as-built drawings.
(b) The documentation for the CQk program for the construction
of the unit should be kept on-site in the facility operating record.
B. Discussion
Construction quality assurance (OQA) during construction of the double-
liner system is essential to assure, with a reasonable degree of certainty,
that the system meets the design specifications. This involves inspecting
and documenting the quality of materials used and the construction practices
employed in their placement. CQA serves to detect deviation from the design
caused by error or negligence on the part of the construction contractor,
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and to allow for suitable corrective measures before wastes are disposed.
Without proper ccnstruction quality assurance, problems with the leachate
collection system(s), and FML top and. conposite bottom liners due to construction
may not be discovered until the system fails during operation.
A recent survey of hazardous waste surface impoundment technology has
found that rigorous quality assurance is necessary to achieve good unit
performance (Ghassemi, et al 1984). Liner failures at several impoundments
were attributed to various factors including "failure to execute proper
quality assurance and control." The success of surveyed facilities that have
performed well is attributed to many factors including "the use of competent
design, construction, and inspection contractors, close scrutiny of all
phases of design, ccnstruction, and QA inspection by the owner/operator,
excellent QA/QC and recordkeeping during all phases of the project, and good
cottttunications between all parties involved in constructing the units."
Specific problems that can cause failure of the double-liner system and
that can be avoided with careful construction quality assurance include:
Collection System(s)
'" The use of materials other than those specified in the approved design;
0 Foreign objects (e.g., soil) left in drain pipes, which plug or restrict
flow and may not be removable using currently available maintenance
procedures;
0 Neglecting to install materials at locations specified in the design;
0 Neglecting to follow installation procedures specified in the design;
0 Siltation of drainage material resulting from improper upgradient drainage
during construction and/or careless construction techniques;
0 Improper use of construction equipment causing crushing or misalignment
of pipes;
0 Improper layout of the system, including misalignment of pipe joints
or improper slopes and elevation of pipes; and
0 Use of unwashed gravel or sand in drain layers.
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FML's Used as the Top Liner and as the Upper Component of the Composite
Bottom Liner
8 The use of materials other than those specified in the approved design;
0 Inproper preparation of the supporting surface (usually soil subgrade)
to receive the liner;
0 The use of improper installation techniques and procedures by the
contractor;
0 The improper use of construction tools and equipment;
0 Inadequate sealing and anchoring of the liner to structures, pipes,
and other penetrations through the liner;
0 Installation of the liner during inclement weather; and
0 Improper repair of defects in the installed liner resulting from
manufacturing processes and installation methods.
Low Permeability Soil Layer in Composite Bottom Liner
0 The use of materials other than those specified in the approved design;
0 Improper compaction equipment;
0 Inadequate compactive effort;
0 Inproper compaction procedures;
0 Inadequate scarification between lifts;
0 Excessive lift thickness;
0 Inadequate liner thickness;
0 Excessive field hydraulic conductivity;
8 Inadequate method of water addition;
8 Inadequate time allowed for even distribution of moisture;
8 Inadequate method used to maintain the optimum moisture content in
the liner between construction of each lift and after completion of
the liner; and
0 The use of an inadequate quantity of added fine-grained materials
(important with bentonite/soil liners).
The ability of the hazardous waste disposal unit to meet its designed
regulatory performance goals depends on adherence to approved design plans
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and specifications during construction. Confidence in the ability of the
installed liners to perform properly is attained through a well-developed,
well-implemented, and well-documented CQA program. The program should be
developed by the design engineer, who can focus the enphasis of quality
assurance on those elements of the design that are critical to FML and low-
permeable soil liner performance. Inplementation of the CQA program should
include participation by the design engineer in resolving construction or
design problems that nay be identified during construction. Timely identifi-
cation of such problems during construction allows corrective measures to be
taken before construction is completed and wastes are deposited. Confidence
in the liner is established through:
0 Careful documentation of:
- Construction scheduling, conditions, and progress;
- Site inspections;
- Material/equipment testing results and data verification; and
- As-built conditions.
0 The owner/operator providing the cpportuiiity for review, inspection,
and approval by appropriate regulatory and permitting agencies.
Each of the elements identified as components of the written construction
quality assurance plan will be described in detail in an upcoming document
on the subject of construction quality assurance for hazardous waste land
disposal units entitled, Construction Quality Assurance for Hazardous
Waste Land Disposal Facilities. The document will address the components
listed below:
0 Low permeability soil liners;
0 Flexible membrane liners (FML's) or synthetic membrane liners;
0 Dikes;
0 Low permeability soil caps and cover systems; and
0 Leachate collection systems.
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uUubLL LiNLK
The FML/compacted low permeability soil double liner design consists,
at a minimum, of a primary leachate collection and removal system (for landfills),
an FML top liner designed, operated, and constructed of materials to prevent
the migration of any constituent into such liner during the period the unit
remains in operation (including any post-closure monitoring period), a
secondary leachate collection system, and a bottom liner designed, operated,
and constructed to prevent the migration of any constituent through the
liner during this period (See Figure 7). The bottom liner should consist of
compacted soil with a hydraulic conductivity of 1 X 10"^. The liner should
be of compacted low permeability soil materials rather than in-situ soil
materials. The liner thickness should be calculated using the formulas and
assumptions set out in this section of the guidance and should be three feet
thick at a minimum.
EPA believes that this design will protect human health and the environment
because if liquid appears between the liner, the compacted soil clay bottom
liner provides for removal of some leachate by the leachate collection
system and infiltration of the remaining leachate into the liner. The liner
is designed to be of sufficient thickness to prevent migration during the
period of facility operation, including the post-closure monitoring period.
Section 3004(o) (5) (B) provides that, until the effective date of EPA
regulations implementing Section 3004 (o) (1)(A), the statutory requirement
for two liners may be satisfied by the installation of a top liner designed,
operated, and constructed of materials to prevent the migration of any
constituent into such liner during the period the facility remains in operation
(including any post-closure monitoring period) and a lower liner designed,
operated, and constructed to prevent the migration of any constituent through
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Materials
Graded Granular Filter Medium
Granular Drain Material
(bedding)
Flexible Membrane Liner (FML)
Granular Drain Material
(bedding)
Low Permeability Soil, Compacted in Lifts
(soil liner material)
Note: FML thickness > 45 mils
recommended if liner is not
covered within 3 months.
FIGURE 7
SCHEMATIC PROFILE OF AN FML/COMPACTED SOIL
DOUBLE LINER SYSTEM FOR A LANDFILL
Dimensions and Specifications
6 Odo° ?.:•?<> ? <> V
Recommended Thickness > 6 in.
Maximum Head on Top Liner = 12 in.
Recommended Thickness > 12 in.
Hydraulic Conductivity > IxlO"2 cm/sec
, Drain Pipe
O
Recommended Thickness of FML > 30 mils (see note)
Recommended Thickness > 12 in.
Hydraulic Conductivity > 1x10 2 cm/sec
Drain Pipe
o
Thickness Determined by Breakthrough Time
Recommended Hydraulic Conductivity < IxlO'7 cm/sec
Unsaturated Zone
l
/. Saturated Zone ///////
////////////////////////////I
Nomenclature
Solid Waste
Filter Medium
Primary Leachate Collection and
Removal System
Top Liner (FML)
Secondary Leachate Collection and
Removal System
Bottom Liner (compacted low permeability soil)
Native Soil Foundation/Subbase
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53
such liner during this period. Section 3004(o)(5)(B) also provides that a
lower liner shall be deemed to satisfy this requirement if it is constructed
of at least a 3-foot thick layer of conpacted clay or other natural material
with a permeability of no more than 1 x 10~^.
The Agency's EML/coirpacted soil double liner design contains the performance
standards set out in the statute. The inportant difference between the Agency's
design and the statutory interim standard is that three feet of reconpacted
clay will satisfy the statutory requirement, while three feet is the minimum
recommended thickness in the Agency's design. Until EPA issues regulations
implementing the statute, EPA will accept a bottom liner design of three
feet of compacted clay or other natural material with a permeability of no
more than 1 x 1CT7. However, the Agency believes that this bottom liner
will not in practice meet the requirement to prevent migration of any constituent
through the liner during the operational period. EPA believes that owners
and operators who wish to install a clay lower liner should consider three
feet as a minimum thickness and use this guidance to determine the recoranendea
thickness.
In order to meet this performance standard, both the top and bottom
liner should be chemically resistant to the waste and leachate managed at the
unit. In addition, these liners should be constructed of materials that
have appropriate properties and sufficient strength and thickness to prevent
both structural and chemical failure caused by factors which include material
aging and the stresses of construction and operation.
The top liner must be a FML material that meets the requirement that
constituents not migrate into the liner. EPA's recommended bottom liner
design is:
(1) That it consist of a minimum three feet of conpacted soil with a
hydraulic conductivity of 1 X 10~7 cm/sec or less; and
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59
(2) That it be sufficiently tliick so as to prevent any constituent from
migrating through the bottom of the conpacted soil liner prior to
the end of the post-closure monitoring period.
Until the effective date of regulations inpleinenting section 3004(o) (1) (A),
EPA will accept a three foot bottom liner. However, EPA believes that in
practice a bottom liner consisting of three feet of compacted soil with a
hydraulic conductivity of 1X10"^ cm/sec will not meet the second standard
listed above. In the case of a saturated soil, low effective porosity values
may allow the early release of constituents. In the case of an unsaturated
soil, capillary forces may draw constituents through the liner prior to the
end of the post-closure monitoring period. Therefore, EPA recomnends that
an owner or operator who wishes to install a bottom compacted low permeability
soil liner use this guidance to determine the thickness of the bottom liner.
Methods tliat have been suggested for modifying a compacted soil liner to
weet the recommended standard are as follows:
(1) Decrease its permeability; and/or
(2) Increase its thickness.
Either of these ways of modifying the liner could theoretically result in a
liner that would prevent migration for the combined active life and 30 year
post-closure monitoring period of a facility (usually a total of 40-50 years).
The Agency does not discourage rigorous demonstrations of compacted low
permeability soil liner designs that would meet the recommended standard.
The Agency has, however, strong reservations concerning the likelihood that
such a design is either economically or technically feasible. Some of the
issues underlying these reservations are as follow:
(1) There are no clear criteria or techniques available for making
breakthrough determinations. While several methodologies have been suggested,
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60
the Agency is not aware of any methods which have undergone rigorous field-
verification testing.
(2) It is not clear whether it would be economically feasible to construct
a low permeability soil liner thick enough to prevent breakthrough for over
40 years assuming adequate flow from the overlying landfill or surface impoundment
to maintain continuous unsaturated (capillary) flow through the soil liner
during that period. Recent computer models of unsaturated flow through
compacted liners suggest that assuming continuous flow through the liner,
a liner may need to be much greater tlian 10 feet thick even at hydraulic
conductivities substantially less than 1 X 10~"7 on/sec.
(3) Hydraulic conductivities of 1 X 10"? cm/sec or less have not been
routinely and consistently obtained in the past on an overall in-field scale
liner system. A number of studies have suggested that actual field scale
hydraulic conductivities may be in the range of 10 to 1000 times higher than
the 1 X 10~7 to 1 X 10~8 cm/sec values that are routinely obtainable in
laboratory tests. The Agency believes that if a testfill (described in the
section on construction of low permeability soi\) is used, a hydraulic conductivity
of 1X10~7 can be achieved in the liner.
(4) The capability of current testing methods to verify with a high
degree of confidence the actual field performance of a compacted low permeability
soil liner has not been demonstrated. Consequently, the Agency currently
believes that the best method would include construction of a test fill and the
collection of field hydraulic conductivity data.
Test fills have been used by the geotechnical engineering community to
evaluate the design of soil liners used in cooling ponds for the nuclear
power industry. Test fills have also been used during the design stage of
dams to obtain information on engineering properties of the compacted soil
such as density, strength, and hydraulic conductivity (Barren, 1977). Construction
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61
control of test fills must be very strict and well documented or the data
obtained will be of questionable value (Corps of Engineers, 1977).
Field hydraulic conductivity tests have been found to give a much more
accurate assessment of the hydraulic conductivity of conpacted soil liners
(Daniel, 1984; Day 1984). Field tests conducted in a test fill should be an
effective and accurate method to predict the overall saturated hydraulic
conductivity of a compacted soil liner. Both test fills and field hydraulic
conductivity tests are discussed in greater detail in Section II of this
guidance document.
The time required for liquid to breakthrough a conpacted soil liner will,
in most cases, be initially governed by unsaturated liquid flow through the
liner. During the early stages of wetting of a conpacted liner, capillary
attraction forces predominate over gravitational forces. As a compacted
liner becomes wetter, the capillary forces would decrease in importance. In
a saturated liner, capillary forces are negligible in comparison to gravitational
forces.
To accurately and reliably estimate the t^ae to breakthrough for a given
liner thickness, a field verified equation is required that accounts for
effective porosity, water content, capillary forces, and unsaturated hydraulic
conductivity at various depths in the liner over time. Unsaturated hydraulic
conductivity measurements are both difficult and not routinely performed by
soil engineering laboratories. The task of documenting unsaturated hydraulic
conductivity values for a compacted low permeability soil liner at several
water contents would indeed be difficult on even a small laboratory scale.
In addition, the Agency is not aware of any field scale studies to verify
laboratory-derived unsaturated hydraulic conductivity values.
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62
The Agency is studying the breakthrough of constituents through compacted
low permeability soil liners. There is currently however, no field verified
method for determining either breakthrough or the associated liner thickness
requirements. Using the draft computer model which is currently in development
and as yet not field tested (SOILINER), the interim design (i.e., a three
foot thick compacted liner with a saturated hydraulic conductivity of 1X1CT7
cm/sec) representing a landfill scenario with a one foot head above the liner
results in a breakthrough time of approximately three years (Johnson and
Wood, 1984). Assuming adequate flow from the overlying landfill or surface
impoundment to maintain continuous unsaturated (capillary) flow through the
soil liner during the operating and post-closure period, a compacted liner
would need to be at least several times this thickness or be of a lower
order of permeability in order to prevent breakthrough of mobile waste
constituents during the 40 to 50 years most surface impoundments and landfills
will be operated, including the post-closure monitoring period.
The draft computer model discussed above has been published by the EPA
(1984B). The Agency plans to update this model and evaluate further the
appropriateness of it for use in estimating the thickness requirements or
breakthrough time for compacted liners.
Conservative assumptions should be used in estimating the compacted
low permeability soil liner thickness because of the lack of precision
with which such estimates can be made. There are several difficult to
estimate variables that affect the thickness needed to prevent migration
of hazardous constituents over the operational life of the soil liner.
Examples of the conservative assumptions that should be used to estimate
soil liner thickness are as follows:
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63
1. Breaches develop in the top FML during the first year of operation.
Even with a rigorously implemented construction quality assurance plan,
it is not possible to be 100% certain'that all defects initially present in
the FML have been detected. In addition, weak seams may open up shortly after
installation due to operational stresses (e.g., overburden pressures that
occur during the initial placement of wastes). Equipment is more likely to
damage the FML shortly after installation because there may only be a leachate
collection layer between the equipment and the liner.
2. The leakage/impingement rate of leachate to the soil liner should be
based on an estimate of active life and post-closure (for disposal
units) conditions.
For landfills during the active life the leakage into the compacted
soil liner should be based on the rate of moisture/liquid infiltration into
the landfill considering (1) leachate collection and removal by the primary
leachate collection system under proposed removal conditions, (2) leachate
leakage through potential top liner failure conditions, (3) leachate collection
and removal by the secondary leachate collection system, and (4) the compacted
soil liner surface conditions. Failure conditions for the top liner should
consider data from existing similar units currently in operation when available.
The failure conditions should consider all liner breaches that may be expected
to occur during construction, active life, and the post-closure monitoring
period of the unit. Even small leaks in the FML could allow a steady supply
of leachate to a portion of the compacted soil liner. The type of failures
that should be considered (i.e., seam failures, punctures, rips, tears,
chemical compatability) are addressed in the U.S. EPA Technical Resource
Docunent Lining of Waste Impoundments and Disposal Facilities, SW-870, March 1983.
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64
If the owner or operator agrees to repair breaches in the liner during
operation or other time periods then repair can be included as part of the
calculation. The repair assumptions in the calculation should be representative
of actual repair operating practices.
Unless data is available to demonstrate that the top liner will have zero
leakage throughout the operating life of the unit (including the post-closure
monitoring period) a very small leakage rate should be assumed to occur when
leachate is in the primary leachate collection system.
For surface iinpoundments during the active life the leakage rate into
the compacted soil liner should be based on (1) the maximum designed operating
head for the impoundment, (2) leakage through potential top liner failure
conditions, (3) leachate collection and removal by the secondary leachate
collection system, and (4) the compacted soil liner surface conditions. The
top liner failure conditions that should be considered are discussed above
under landfills.
During the post-closure monitoring period the leachate impinging on the
primary leachate collection system for a landfall or top liner in a surtace
impoundment should represent 1) the effectivness of the final cover in minimizing
precipitation infiltration during the post-closure monitoring period and 2)
drainage from the waste resulting from precipitation that was intercepted by
the waste during the active life, and leachate that is generated from decornposit
of the organic waste constituents.
3. The post-closure monitoring period should be at least 30 years.
Current Subpart G requirements are for post-clsoure care to "continue for
30 years after the date of completing closure". This time frame is considered
by EPA to be a minimum estimate of how long the waste will remain hazardous.
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65
4. Leakage from potential top liner failure conditons would occur throughout
the operation period unless the owner or operator agrees to repair the
breaches.
As discussed in assumption Number 2, there are several ways leachate can
form during the operational period of the unit.
5. Nature and quantity of the waste should be considered.
Volume of leachate released by the waste as deconposition by-products
will depend on the total organic content of the waste. The higher the organic
content of a waste, the greater would be the fraction of the waste which
could be liquify during its deconposition. The total quantity of organic
materials in the facility would affect the total volume of leachate that
could eventually be generated fron deconposition of the waste.
Composition of a waste will affect the conposition of the leachate.
High concentrations of certain leachate ccnponents may increase the rate at
which a soil liner transmits leachate (Anderson, 1982). If the leachate
has a flow rate through the compact soil liner faster than water this should
also be considered in the evaluation of required liner thickness.
6. Any allowance for attenuation of the waste constituents by the soil
liner should take into account the nature of the waste and any factors
that may reduce attenuation.
Some waste constituents (such as cations) can be strongly attenuated by-
soils under ideal conditions (EPA/ 1983C). The effect is difficult to quantify
but may be considered in limited cases such as some monofills. The demons tr a tic,-
of acceptability should be based on data from field tests. The extent to
which many of these are attenuated can, however, be greatly decreased in the
acidic and anaerobic conditions that are often present near soil liners.
Other waste constituents (such as anions) may not be appreciably attenuated
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66
by soil. Movement of waste constituents will also be affected by the effective
porosity of the soil liner. There are a number of other conditions under
which attenuation can be greatly reduced. In addition, the conditions that
optimize attenuation of one constituent may promote leaching of another
(Lindsey, 1979).
7. The effective porosity would be 0.05.
Total porosity of a compacted soil will usually be less than 0.5 (Anderson
et al., 1984; and Brown and Anderson, 1983). Effective porosity can be much
less than total porosity in fine-grained soils (Gibb et al., 1985). Green
et al, (1985) found that in some compacted samples only 10% of the total
porosity was effective in transmitting liquids. Ten percent of even the
highest total porosity likely in a compacted specimen would result in an
effective porosity of no greater than 0.05.
8. The compacted low permeability soil liner and adjacent soil strata
would be initially unsaturated.
Design criteria given elsewhere in this document state that the liner
system for the two designs should be construct^ completely above the seasonal
high water table (i.e., in unsaturated soil). Under these conditions, the
soil strata immediately adjacent to the liner would probably also be unsaturated.
The owner/operator should fully document methods used to evaluate the necessary
liner thickness. These evaluations should also address at least the following:
(1) Horizontal hydraulic conductivity within and between the individual
lifts (Brown et al, 1983 Boynton, 1983);
(2) Variability in the hydraulic conductivity of the compacted soil
liner in the field (Daniel, 1984);
(3) The potential for long term changes in hydraulic conductivity
resulting from loss of moisture by the liner due to climatic conditions
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67
or the equilibrium moisture content in the adjacent soil deposits; and
(4) The effect of liner aging on the long-term equilibrium hydraulic
conductivity of the liner (Mitchell et al, 1965; Dunn and Mitchell
(1984); Boynton, 1983).
Under this approach to bottom liner design, the leachate collection and
removal system between the two liners must be: (1) capable of detecting,
collecting, and removing liquids in case leaks develop in the primary liner,
(2) constructed of materials that can withstand the chemical attack that
results from wastes or leachates, (3) capable of withstanding the stresses
and disturbances from overlyinq wastes and operating practices, and (4)
operated to collect and remove liquids through the operating period, including
the post-closure monitoring period.
The collection system between the two liners should comply with the
guidance contained in Section III of the Synthetic/Composite Double Liner
System. For landfills, the leachate collection and removal system above the
top liner should comply with the guidance contained in Section I of the
Synthetic/Composite Double Liner System. The t-'.p liner should comply
with the guidance contained in section II. The bottom liner should comply
with the relevant portions of section II dealing with the compacted lower
component of the composite liner. Section IV, on Construction Quality Assurance,.
should be used to assure that the completed double liner system meets the
design criteria and specifications.
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68
References
Anderson, D.C. (1982), Clay Liner-Hazardous Waste Conpatibility. Report to
the U.S. EPA, K.W. Brown and Associates, College Station, Texas. (EPA
Contract # 68-01-6515)
Anderson, D.C., J.O. Sai, and A. Gill (1984), Surface Impoundment Soil
Liners: Permeability and Morphology of a Soil Liner Permeated by Acid and
Field Permeability Testing for Soil Liners. Report to U.S. EPA, K.W.
Brown and Associates, College Station, Texas. (EPA Contract # 68-03-2943)
August, H., R. Tatzky, G. Pastuska, and T. Wift. (1984), Study of the Permeation
Behavior of Commercial Plastic Sealing Sheets as a Bottom Liner for Dumps
Report No. 103 02 208, Federal Minister of the Interior, Berlirr, West Germany.
Barren, R.A. (1977), The Design of Earth Dams. (Chapter 6) In (A.R. Golze,
ed) Handbook of Dam Engineering. Van Nostrand Reinhold Company, N.Y. p.
291-318.
Boutwell, G.P. and V.R. Donald (1982), Compacted Clay Liners for Industrial Waste
Disposal, Presented ASCE National Meeting, Las Vegas, April 26, 1982.
Boynton, S.S. (1983), An Investigation of Selected Factors Affecting the
Hydraulic Conductivity of Compacted Clay. M.S. Thesis, University of
Texas, Geotechnical Engineering Thesis GT83-4, Geotechnical Engineering
Center, Austin, Texas. 79 p.
Boynton, S.S. and D.E. Daniel (1985), Questions Concerning Hydraulic Conductivity
of Compacted Clay. Journal of Geotechnical Engineering, Vol. Ill, No. 4.
Brown, K.W. and D.C. Anderson. (1983), Effects of Organic Solvents on the
Permeability of Clay Soils. United States Enviromental Protection Agency.
Grant No. R806825010. 153 p.
Brown, K.W., J.W. Green, and J.C. Thomas, J.C. (1983), The Influence of Selected
Organic Liquids on the Permeability of Clay Liners, In Proceedings of
the Ninth Annual Research Symposium on Land Disposal of Hazardous Waste,
(EPA-600/9-83-018). p. 114-125.
Corps of Engineers (1977), Earth-fill and Rock-fill Construction. (Chapter 5)
In Construction Control for Earth and Rock-Fill Dams. U.S. Arny Engineer
Manual EMI 110-2-1911
Daniel, D.E. (1984), Predicting Hydraulic Conductivity of Clay Liners.
Journal of Geotechnical Engineering, Vol. 110, No. 2 p. 285-300.
Daniel, D.E., D.C. Anderson and S.S. Boynton (1985), Fixed-Wall vs Flexible-Wall
Permeameters. _In Hydraulic Barriers in Soil and Rock, ASTM STP 874 (In
Press).
Day, S.R. (1984), A Field Permeability Test for Compacted Clay Liners. M.S.
Thesis, University of Texas, Austin, Texas 105 p.
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69
Day, S.R., D.E. Daniel, and S.S. Boyriton, (1985), "Field Permeability Test
for Clay Liners. In Hydraulic Barriers in Soil and Rock, ASTM STP 874
(In Press).
Dunn, R.J. and J.K. Mitchell (1984), Fluid Conductivity Testing of Fine-Grained
Soils. Journal of Geotechnical Engineering, Vol. 110, No. 11, p. 1648-1665.
Earth Manual. (1984), Bureau of Reclamation, U.S. Department of the Interior.
Government Printing Office, Washington, D.C.
EPA (1982), Test Methods for Evaluating Solid Waste. United States Environmental
Protection Agency, Washington, D.C. (SW-846).
EPA (1983), Landfill and Surface Impoundment Performance Evaluation United
States Environmental Protection Agency/ Washington, D.C. (SW-869), April 1983.
(S/N 055-000-00233-9, $5.00), Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402, 69 pages.
EPA (1983A), Lining of Waste Impoundment and Disposal Facilities. United States
Environmental Protection Agency, Washington, D.C. (SW-870), March 1983.
(S/N 055-000-66231-2, §11.00), Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402, 448 pages.
EPA (1984B), Procedures for Modeling Flow Through Clay Liners to Determine
Required Liner Thickness. (Draft Technical Resource Document for Public
Comment) United States Environmental Protection Agency, Washington, D.C.
(EPA/530-SW-84-001). 32 p.
EPA (1984A), Soil Properties, Classification, and Hydraulic Conductivity
Testing. United States Environmental Protection Agency, Washington, D.C.
(SW-925). 167 p.
EPA (1983C), Hazardous Waste Land Treatment, f'.iited States Environmental
Protection Agency, Washington, D.C. (SW-874).
Geotextile Engineering Manual, Training Manual, Federal Highway Administration.
Ghassemi, M., M. Haro, and L. Fargo (1984), Assessment of Hazardous Waste
Surface Impoundment Technology Case Studies and Perspective of Experts.
Report to the U.S. EPA, MEESA, Torrance, CA. (EPA Contract #69-02-3174),
Green, J.W., K.W. Brown, J.D. Thomas (1985), Effective Porosity of Compacted
Clay Soils Permeated with Organic Chemicals. _In Land Disposal of Hazardous
Waste, Proceedings of the Eleventh Annual Research Synposium, pp. 270-271.
Griffin, R.A. et al. (1984), Migration of Industrial Chemicals and Soil-waste
Interactions at Wilsonville, Illinois. _In_ Proceedings of the Tenth Annual
Research Symposium on Land Disposal of Hazardous Waste (EPA 600/9-84—007)
USEPA Municipal Environmental Research Laboratory, Cincinnati, OH 45268.
Griffin, R.A., N.F. Shrimp, Attenuation of Pollutants in Municipal Landfill
Leachate by Clay Minerals, EPA-600/2-78-157, U.S. EPA, MERL, Cincinnati, OH
[OTIS PB 287-140/AS].
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70
Griffin, R.A., R.E. Hughes, L.R. Polluter, C.J. Stohr, W.J. Morse, T.M. Johnson,
J.K. Bartz, J.D. Steele, K. Cartwright, M.M. Killey and P.B. DuMontelle
(1984), Migration of Industrial Chemicals and Soil-Waste Interactions at
Wilsonville, Illinois. In: Proceedings of the Tenth Annual Research
Symposium on Land Disposal of Hazardous Waste, (EPA 600/9-84-007)'.
Herzog, B.L. and W.J. Morse (1984), A Corrparison of Laboratory and Field
Determined Values of Hydraulic Conductivity at a Waste Disposal Site. In:
Proceedings of the Seventh Annual Madison Waste Conference, University of
Wisconsin-Extension, Madison, Wisconsin, pp 30-52.
Horz, R.C. (1984), Geotextiles for Drainage and Erosion Control at Hazardous Waste
Landfills. EPA Interagency Agreement No. AD-96-F-1-400-1. U.S. EPA,
Cincinnati, Ohio.
Johnson, Russell and Eric Wood, (1984), Unsaturated Flow Through Clay Liners.
Report to the U.S. EPA, GCA Corporation, Bedford., MA. (EPA Contract
#68-01-6871).
Johnson, Russell and Eric Wood, (1984), Unsaturated Flow Through Clay Liners
(Letter Report). Prepared for the Office of Solid Waste, Washington, D.C.,
GCA Corporation, Bedford, NA. (GCA-TR-85-01-G) 29 p.
Kays, W.B. (1977), Construction of Linings For Reservoirs, Tanks, and Pollution
Control Facilities. John Wiley & Sons, Inc. NY. 379 p.
Koerner, Robert M., and J.P. Welsh (1980), Construction and Geotechnical Engineering
Using Synthetic Fabrics. John Wiley and Sons, New York.
Lindsey, W.L. (1979), Chemical Equilibria in Soils. John Wiley and Sons, Inc.,
449 p.
Mitchell, J.K. (1976), Fundamentals of Soil Behavior. John Wiley arid Sons,
Inc., N.Y. 422p.
Mitchell, J.K., D.R. Hooper, and R.G. Canpanella (1965), Permeability of
Compacted Clay. Journal of the Soil Mechanics and Foundations Division,
ASCE, Vol. 91, No. SM4. p. 41-65.
NSF (1983), Standard Number 54, Flexible Membrane Liners. National Sanitation
Foundation, Ann Arbor, Michigan. 69p.
?
Olson, R.E. and D.E. Daniel (1981), Field and Laboratory Measurement of the
Permeability of Saturated and Partially Saturated Fine-Grained Soils. .In
Permeability and Groundwater Contaminant Transport, ASTM STP 746.
U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604 ;
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71
Suggested Reading List
Flexible Membrane Liner Permeation
Haxo, H. E., J. A. Miedema, and N. A. Nelson (1984), Permeability of Polymeric
Membrane Lining Materials for Waste Management Facilities. In Proceedings
of the Education Symposium on Migration of Gas, Liquids, and Solids in Elastomers,
Denver, Colorado. Sponsored by Rubber Division, American Chemical Society,
Oct. 23-26, 1984.
August, H., R. Tatzky, G. Pastuska, and T. Win (1984), Study of the Permeation
Behavior of Commercial Plastic Sealing Sheets as a Bottom Liner for Dumps
Against Leachate, Organic Solvents, and their Aqueous Solutions. Research
Report No. 103 02 208, Federal Minister of the Interior, Berlin, West Germany.
Mitchell, J. K., D. R. Hooper, and R. G. Campanella, (1965), Permeability of
Compacted Clay. Journal of Soil Mechanics Foundation Division, ASCE, 91 (SM4):
41-65.
Statistical earthwork control
Hinterkorn, H., and H. Y. Fang. Foundation Engineering Handbook, Van-Nostrand-
Reinhold, Publishers (1975), See Chapter 7 by Jack W. Hilf, section 7.4:
Control of Compaction.
Lee, I. K., W. W-iite, and O. G. Ingles. Geotechnical Engineering, Pitman Publishers
(1983), See Chapter 2, Soil Variability; and Chapter 9, Soil Treatment:
Quality Assurance. (Good general introduction to the use of statistics).
Representative samples
U.S. Environmental Protection Agency. Test Methods for the Evaluation of
Solid Waste. SW-846, Washington, D.C., July 1982 Second Edition.
U.S. Environmental Protection Agency. Draft Solid Waste Leaching Procedure
Manual. Washington, D.C., 1983.
Graded granular filters
U.S. Environmental Protection Agency. Guide to the RCRA Land Disposal Permit
Writers' Training Program, Volume 1, Sept. 1984, Chapter 3, p. 3-38 to 3-41.
Synthetic fabric filters
U.S. Environmental Protection Agency. Guide to the RCRA Land Disposal Permit
Writers's Training Program, Volume 1, Sept., 1984, Chapter 3, p. 3-44 to 3-46.
U.S. Federal Highway Administration. Geotextile Engineering Manual.
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