United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/&30/SW 86/00?F July 1990
EPA Project Summary
Design, Construction, and
Evaluation of Clay Liners for
Waste Management Facilities
L. J. Goldman
This Technical Resource Document Is
a compilation of available Information
on the design, construction, and evalu-
ation of clay liners for waste landfills,
surface Impoundments, and waste-
piles. The Information was obtained
from the literature and from In-depth
interviewswlth design and construction
engineers and other knowledgeable
Individuals in both the private and gov-
ernment sectors. As a consequence,
some of the Information is being pre-
sented In print for the first time In this
document. The broad topics covered
are: clays, with emphasis on their com-
position, fabric, and hydraulic conduc-
tivity; the compatibility between clays
and chemicals, including a discussion
of the mechanisms of Interaction and a
comprehensive compilation of test data
from the literature and private, unpub-
lished sources; design and construc-
tion methodology and construction
quality assurance; and clay liner transit
time prediction models. The technical
resource document also incorporates
public comments received on a draft
that was published in 1986.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
Is fully documented In a separate report
of the same title (see Project Report
ordering Information at back).
Introduction
The U.S. Environmental Protection
Agency (EPA) is developing three types of
documents for preparers and reviewers of
permit applications for hazardous waste
facilities. These are RCRA Technical Guid-
ance Documents, Permit Guidance Manu-
als, and Technical Resource Documents
(TRDs).
The TRDs present state-of-the-art sum-
maries of the technologies and evaluation
techniques determined by EPA to consti-
tute good engineering practices, designs,
and procedures. They support the RCRA
Technical Guidance Documents and Per-
mit Guidance Manuals in certain areas (i.e.,
liners, leachate management, closure cov-
ers, and water balance) by describing cur-
rent technologies and methods for design-
ing hazardous waste facilities or for evaluat-
ing the performance of a facility design.
Although emphasis is given to hazardous
waste facilities, the information presented
in these TRDs may be applied to nonhaz-
ardous waste facilities as well.
This is a TRD prepared by the Risk Re-
duction Engineering Laboratory of the Of-
fice of Research and Development at the
request of and in cooperation with the
Office of Solid Waste and Emergency
Response. The TRD was first issued as a
draft for public comment under the title,
Design, Construction, and Evaluation of
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Clay Liners for Waste Management Facili-
ties (EPA/530-SW-86-007) dated March
1986, The draft TRD was also made avail-
able through the National Technical Infor-
mation Service (Order No. PB86-184496/
AS). All comments received on the draft
TRD have been carefully considered and, if
appropriate, changes were made in this
final document to address the public's
concerns. With issuance of this document,
all previous drafts of the TRD are obsolete
and should be discarded.
The objective of this TRD was to provide,
in a single document, all of the available
information on the design, construction,
and performance of clay lined waste man-
agement facilities. The broad topics that
were covered are: clay properties and char-
acteristics (chapter 2); geotechnical testing
of soils (chapter 3); the compatibility of
clays and chemical wastes (chapter 4); the
design, construction, and construction
quality assurance of clay liners (chapters);
potential failure mechanisms (chapter 6);
the performance of existing liner systems
(chapter 7); and methods of predicting the
useful life of liner systems (transit time)
based on the modeling of leachate flow
through soils (chapter 8).
Discussion
Chapter 2 of the TRD contains a general
discussion of the structure of clay soils and
continues on to a discussion of the main
types of clay minerals (e.g., kaolinite, illite)
and how clay soils were formed. A section
on clay chemistry deals with the electrical
double layer theory, cation-exchange ca-
pacity, and cation affinity. A short discus-
sion of the significance of the double layer
theory to clay liners is also included. Other
subjects discussed are related to clay soil
fabric and hydraulic conductivity. These
include soil porosity, macrostructure and
secondary porosity, and the structure and
hydraulic conductivity of compacted soils.
The third chapter presents the soil test
methods currently used in the design and
construction of clay liner systems. The
chapter starts with a discussion of the
fundamental relationships between the
solid, liquid, and air phases of soil systems.
The Atterberg limits and the methodology
for determining them are discussed. The
Unified Soil Classification System is pre-
sented in sufficient detail to provide the
nontechnical reader with an understanding
of how the system works. In the section on
measuring density and moisture content in
the field, the traditional methods are pre-
sented along with a detailed discussion of
nuclear density gauges and the problems
that can be encountered in their use on
certain soils. Much of the chapter is de-
voted to describing the current methodolo-
gies employed in measuring the hydraulic
conductivity of compacted clay soils in the
laboratory and in the field. Included is a dis-
cussion of factors that can influence the
results of permeability tests. The field per-
meability testing section contains descrip-
tions of several new tests that have recently
been introduced and thus have not been
extensively discussed in the open literature.
In the fourth chapter, "Interactions Be-
tween Clays and Chemicals", the mecha-
nisms of the interactions, and the effect
they have on permeability are discussed.
The bulk of the chapter presents the results
of published and unpublished research
studies, some of which are published forthe
first time in this document, having been ob-
tained from the files of private soil testing
firms. The studies are summarized in a
large table organized on the basis of the
chemical or waste stream that was tested.
This table quickly references the effect that
a given chemical can have on specific
clays.
The fifth chapter of the document is a
detailed discussion of the current practices
employed in the design and construction of
clay liner systems. Much of the information
was obtained from interviews with design
and construction professionals and ap-
pears in print for the first time in this TRD.
All aspects of liner design and construction
are discussed including site investigation,
liner material selection, facility design, clay
liner installation, and quality assurance and
quality control.
Chapter 6 covers the mechanisms that
potentially cause clay liner systems to fail.
Mechanisms such as desiccation cracking,
slope instability, freeze/thaw cycling and
others are discussed theoretically, since
there is little hard evidence to suggest which
if any of these are consistent sources of
failure in clay lined systems.
Information about the performance of clay
liners is contained in chapter 7, which is a
presentation and analysis of 17 case stud-
ies. The data for the sites were obtained
from state and federal agencies, commer-
cial waste disposers, clay liner design and
construction firms, and the industrial sec-
tor. The information presented for each site
includes geological and hydrogeological
site characteristics, types of waste in the
site, geotechnical characterization of the
clay, leachate collection, leak detection, or
groundwater monitoring data, physical
description of the site, liner description,
construction methods used in building the
liner.
Methods for predicting the useful life of a
liner are described in chapter 8. Several
mathematical models are presented for
predicting the transit time of leachate
through a compacted clay liner.
The full report was submitted in fulfillment
of Contract No. 68-01-7310 by NUS Corpo-
ration underthe sponsorship of the U.S. En-
vironmental Protection Agency.
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LJ. Goldman is with the NUS Corporation, Gaithersburg, MD 20878.
Michael Roullar is the EPA Project Officer (see below).
The complete report, entitled "Design, Construction, and Evaluation of Clay Liners for
Waste Management Facilities" (Order No. PB89-181 937/AS; Cost: $49.95) will be
available only from:
National Technical Information Service
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
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