United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory . _ .
Cincinnati OH 45268 ' "i *
Research and Development
EPA-600/S2-83-109 Feb. 1984
4>ERA Project Summary
Potential Clogging of Landfill
Drainage Systems
Jeffrey M. Bass, John R. Ehrenfeld, and James N. Valentine
The potential clogging of landfill
drainage systems was investigated with
particular emphasis on hazardous sites.
The study accomplished five basic
tasks: (1) to provide general background
on the subject of drain clogging; (2) to
investigate some cemented materials
found in a drain at a landfill in Boone
County, Kentucky, and to determine
possible causes; (3) to examine the
potential for clogging in hazardous
waste leachate collection systems; (4)
to identify preventive or remedial
techniques for drain clogging; and (5) to
identify avenues or research and devel-
opment that might minimize the like-
lihood or impact of clogging.
Study results indicate that clogging is
likely to occur in a probabilistic manner
during the active and post-closure
operational lifetime of a hazardous
waste landfill, but preventive and
remedial techniques can be used to
avoid or mitigate clogging. Preventive
methods (including increased safety
factors or redundancy in design, moni-
toring, periodic inspection.and mainte-
nance) are far superior to remedial
techniques. Repair or replacement is
expensive and potentially dangerous in
the hazardous environment at secure
landfills. Present regulations for hazard-
ous waste landfills provide no guidance
on engineering, design, or operational
practices to prevent clogging or remedy
a malfunctioning system.
This Project Summary was developed
by EPA's Municipal Environmental
Research 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
Clogging caused by a variety of mechani-
sms is common to drainage systems of all
kinds — agricultural irrigation, sanitary
landfills, septic system leach fields, etc.
Concern is particularly great over the
potential clogging of leachate collection
systems in hazardous waste landfills. Not
only are the consequences of failure
much higher at a hazardous waste site,
but excavation and replacement are no
longer simple last resorts.
In response to this concern, this report
investigates the potential clogging of
landfill drainage systems with particular
emphasis on hazardous waste sites. The
study was designed to accomplish the
following tasks:
1. To provide general background on
the subject of drain clogging;
2. To investigate cementitious materi-
als found in gravel around a drain at
a U.S. Environmental Protection
Agency demonstration sanitary
landfill in Boone County, Kentucky,
and to determine possible causes;
3. To examine the potential for clog-
ging in hazardous waste leachate
collection systems;
4. To identify and describe potentially
useful preventive or remedial techni-
ques to avoid, minimize, or eliminate
drain clogging; and
5. To identify fruitful avenues for
research and development to mini-
mize the likelihood or impact of
clogging.
The study was initiated with a
literature review of field experience
and a limited laboratory study of the
materials recovered from the Boone
County Landfill.
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Information Base
To assess the potential for clogging of
leachate collection systems, information
was obtained from the following areas:
1. Regulations to the Resource Con-
servation and Recovery Act (RCRA),
2. Design of leachate collection sys-
tems,
3. Leachate characteristics,
4. Mechanisms of drain clogging, and
5. Relevant experience.
Literature from related fields such as
agricultural drainage and irrigation
systems provided most of the background
because information and direct experi-
ence with leachate collection systems in
general is sparse. Although many differ-
ences exist between conditions of
leachate drains and other kinds of drains,
basic mechanisms leading to clogging are
similar in all systems. In particular, a
paper prepared for EPA by GCA Corpora-
tion (C.W. Young, T.J. Nunno, M.R.
Jasinski, D.R. Cogley, and S.V. Capone,
"Clogging of Leachate Collection Sys-
tems Used in Hazardous Waste Land
Disposal Facilities," Draft White Paper,
U.S. Environmental Protection Agency,
Washington, D.C. In press) was used as a
starting point for the research in this
report.
Clogging Mechanisms
Clogging mechanisms are occurrences
or natural processes that inhibit the flow
of leachate to or through the leachate
collection system. Such as system at a
landfill is considered to be clogged if it
cannot maintain the leachate depth over
the liner at less that 30-cm limit required
in the RCRA standards. The majortypesof
clogging mechanisms in leachate collec-
tion systems are physical, chemical,
biochemical, and biological mechanisms.
Physical mechanisms are the most
common, most well understood causes of
drain failure. Physical factors tend to
predominate in many drainage system
cloggings, though any combination of
factors might occur. Physical failure can
be due to inadequate capacity, structural
failure, or sedimentation or filtration.
Chemical mechanisms for clogging
involve the formation of insoluble precipi-
tates that are deposited on the surfaces
inside of drain pipes, in openings (slots),
and in the drain-pipe envelopes (gravel
and geotextile filters). The most common
form of chemical buildup is calcium
carbonate. Manganese carbonate (rhodo-
chrosite) and other insoluble forms
(sulfides and silicates) have been found in
clogged or partially encrusted drainage
systems.
Biochemical mechanisms occur when
inorganic precipitates are formed in
conjunction with biological systems in
addition to the other simpler mechanisms.
The principal products resulting from
biochemical mechanisms are iron com-
pounds — Fe(OH)3 or FeS (though
manganese compounds may also be
involved). These compounds are deposit-
ed on pipe surfaces and in the envelope
material. The deposits generally contain
organic material as well in the form of
adherent, sometimes filamentous slimes
and organic complexes.
Biological mechanisms are formed
when organisms grow to fill the intersti-
ces in the drain envelope and interfere
with normal flow of leachate. For such
growth to occur, bacteria must be present
in a supportive environment. Many
bacteria are known to use hazardous
organic chemicals for food and can grow
at the temperature, pH, and oxygen
content found in landfills. Heavy metals
often present in hazardous waste landfills
may be toxic or inhibitory to the clog-form-
ing species.
Analysis of Deposits Found at
the Boone County, Kentucky,
Landfill
When Test Cell 1 of the Boone County,
Kentucky, field site was dismantled in
September 1980 after 9 years of testing,
a section of partially cemented gravel was
discovered in the drain envelope extend-
ing 2.2 to 4.2 m (6.5 to 13.5 ft) from the
collection sump (bulkhead). The discovery
of the cemented section was significant
because the test cell had been constructed
to provide a better understanding of such
processes.
Analyses included a physical examination
of the cement material (scanning electron
microscopy, optical microscopy, and X-ray
diffraction and fluorescence analysis) and a
chemical analysis of the mass to determine
primary chemical constituents. Results of
these studies lead to the preliminary
conclusion that the cement is principally a
calcium-iron-magnesium product containing
significant proportions of carbonate (gas
evolution) and phosphate. In addition, a
relatively large proportion of fine silica
appears to be dispersed in the cement. The
lack of significant X-ray diffraction patterns
suggests that the cement is an amorphous
material rather than composed of discrete
crystalline phases. Little can be said about
the clogging mechanisms at work here, but
carbonate incrustation is likely to have
contributed. The role of iron is not yet clear.
In addition to determining the cement
composition, it is important to know why
the cementation occurred only in a limited
portion 2.2 to 4.2 m (6.5 to 13.5 ft) above
the collection sump of the upper drain. One
explanation is that conditions in the wastes
above that section were different from
those elsewhere, but data are not sufficient
to follow that approach. Differences in
operating procedures during the first 7
months of test cell operation caused leach-
ate to back up in the pipe and could have
caused at least the beginnings of the
cementation. Further investigation is
needed for a more definitive conclusion,
however.
Potential for Clogging at
Hazardous Waste Landfills
The potential for clogging of leachate
collection systems at hazardous waste
landfills is of particular concern since ex-
cavation and replacement are not simple
last resorts (as they are in sanitary land-
fills) and since the consequences of
failure are very high. Unfortunately,
direct assessment of clogging potential at
hazardous waste or sanitary landfills is
difficult because little experience has
been had with modern leachate collec-
tion systems. Thus it is useful to compare
the clogging potential of these systems
with agricultural drainage systems,
where clogging is clearly a serious prob-
lem. Table 1 indicates that relative poten-
tial for clogging of agricultural drains and
leachate collection systems at sanitary
and hazardous waste landfills based on
the major potential clogging mechan-
isms. Crushing problems appear to be
more likely to occur at both hazardous
waste and sanitary landfills, whereas
chemical, biochemical, and biological
clogging appear less likely to occur in
hazardous waste systems. This differ-
ence is primarily due to the lower pH
range and the potential toxicity of chemi-
cal constituents to indigenous bacteria.
Sedimentation and pipe deterioration are
also potential problems in hazardous
waste systems.
Prevention and Remedies
Preventive and remedial measures can
be used to address problems with drain
clogging. Preventive measures are inten-
ded to interrupt the sequence of causal
steps necessary for a clogging mechanism
to occur. Prevention of drain clogging can
be accomplished in the following areas:
— design and construction,
— operation and maintenance,
— waste disposal, and
— treatment.
Remedial measures are intended to
eliminate the clogging problem once it
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Table 1. Relative Potential for Clogging of Leachate Collection Systems
Mechanism
Agricultural
Drains
Sanitary
Landfills
Hazardous
Waste
Landfills
Significant
Differences
fof+, -)
Physical:
Crushing
Sedimentation
Deterioration
Chemical (CaCOa)
Biochemical (Ochre, Fe)
Biological
Compact/on, greater
equipment loading
Less careful design and
construction possible
Chemicals, solvents,
low pH not expected
Lower pH
Toxicity to indigenous
bacteria, lower pH
Toxicity to indigenous
bacteria, lower pH
* = possible, * less likely, and * = more likely.
has occurred. Remedial measures for
clogged drain systems include:
— excavation and replacement,
— physical methods, and
— chemical methods.
Examples of preventive and remedial
measures are presented in Tables 2 and
3.
Conclusions
The following conclusions are based on
information and analyses summarized in
the full report.
1. Based on the analysis presented in
the full report and on past experi-
ence with agricultural drainage sys-
tems, sanitary landfills, and (to a
limited extent) hazardous waste
landfill leachate collection systems,
it is reasonable to expect clogging to
occur in a probabilistic manner dur-
ing the active and post-closure
operational lifetime of a hazardous
waste landfill.
2. Mechanisms that affect other types
of systems are expected to con-
tribute to clogging in hazardous
waste landfills. This study was
limited to an examination of clog-
ging in the drainage system per se —
that is, the pipes, envelope, and out-
let system. {The regulatory defini-
tion of "clogging" as used here could
also involve localized blockages
within the waste mass that rest on
the liner and create leachate head
greater than the permissible limit,
but this potential problem was not
examined in depth.)
3. Landfill operators exhibited a vary-
ing degree of concern over the clog-
ging potential of drainage systems.
Most appeared to view the potential
problem as unimportant in both de-
sign and operational considerations
and felt that conventional practices
should be adequate to prevent or
remedy clogging. Only one source
noted that the prevention and
mitigation of clogging received care-
ful and special attention in their de-
sign and operational considerations.
4. Established preventive and remedial
techniques to avoid or mitigate clog-
ging can generally be used at
hazardous waste sites. Acid flush-
ing should be used with great care,
particularly if cyanides are known to
be present.
5. Preventive methods (including in-
creased safety factors or redun-
dancy in design, monitoring, perio-
dic inspection, and maintenance)
are far superior to remedial tech-
niques. Repair and replacement are
often considered quite practical in
other settings, but they are expen-
sive and potentially dangerous in
the hazardous environment at se-
cure landfills.
6. The present regulations regarding
hazardous waste landfills do not ap-
pear to treat clogging system design
and head buildup with the same
thoroughness and level of detail as
liner design or loss of integrity. The
regulations give substantial discre-
tion to regional administrators with
regard to the drainage system. Nei-
ther the regulations nor other sup-
porting documents provide guid-
ance on engineering, design or op-
erational practices to prevent clog-
ging or remedy a malfunctioning
system.
Recommendations
A number of recommendations for fur-
ther research on leachate collection sys-
tems can be made based on the results of
this study. The recommendations listed
below are given with the understanding
that it is important to integrate technical
solutions with practical experience and
expectations. Technical solutions arising
from laboratory-based research and de-
velopment alone are not likely to be im-
plemented if they are considered too ex-
pensive or too complicated to apply under
existing or future conditions. Conducting
technical research in conjunction with
experience on operating leachate collec-
tion systems can help avoid this problem.
1. Specific design and construction
guides should be developed for
leachate collection systems — simi-
lar, perhaps, to the EPA Technical
Resource Documents, which provide
guidance for the design and con-
struction of liner systems. Such a
guide could be used by the Regional
Administrators in approving facili-
ties, or by the Administrator in
preparing regulations for leachate
collection systems. Aspects of any
of the following recommendations
could also be included in this task.
2. Specific operational procedures should
be developed to prevent clogging.
An effective program of treatment
and maintenance can control the
factors needed for cloging mecha-
nisms to occur and and thereby avoid
the clogging problems. This task
should include a cost analysis of
alternative preventive approaches.
3. Monitoring methods to detect clog-
ging or conditions that promote it
should be developed to anticipate
problems before they become too
serious. Conventional techniques
can be applied from related fields
such as groundwater hydrology, and
new techniques can be developed to
indicate when significant clogging
processes are occurring.
4. A quantitative analysis should be
made of the probability of the
various clogging mechanisms. Spe-
cific preventive and remedial ap-
proaches can then be evaluated in the
context of hazardous waste landfills
to determine their quantitative
effects on clogging potential. This
recommendation would involve
both a paper study and a field
investigation under typical hazard-
ous waste landfill conditions.
5. Methods for preventing and correct-
ing clogs in drain envelopes or filter
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Table 2. Preventative Measures for Drain Clogging
Category
Measure
Factors
Affected
Mechanisms
Affected
Comments
Design and Construction
Operation and Maintenance
Waste Disposal
Treatment
pipe diameter 6"
pipe in protective
cradle, soil cover
sealed Joint construction
corps grain size
distribution criteria
submerged outlet
slope 2 percent
pipe size, estimated
flow
crushing
displacement, slotsize
filter material
anaerobic conditions
flow rate
exercise special care in all design
in design and construction
design for prevention all
capacity
structural
structural, sedimentation
sedimentation
chemical, biochemical
capacity, sedimentation
biochemical, biological
capacity, sedimentation.
structural
all
care during placement crushing, displacement structural
compaction, operation in
vicinity of drain
regular monitoring and all all
inspection of system
cleaning all all
minimize nutrients
dispose biocides, toxics
maintain low pH
avoid solvents, oxidizing
agents
biocides
acid
bacteria
bacteria
bacteria
chemical attact
bacteria
all
biochemical, biological
biochemical, biological
chemical, biochemical,
biological
deterioration
biochemical, biological
all
facilitate remedial measures, maintenance
use high strength pipe
use slotted or perforated pipe
options include graded. 2 or more layers
geotextile, 4" minimum depth
depends also on quantity of flow
manholes, c/eanouts, large pipe, etc.
most important for first lift of waste
identify factors, early stages of
clogging for preventative cleaning
removes potential clogging in early
stages, use flushing, low pressure jet
organics, N and P compounds, other
chemicals
acids, bases, heavy metal wastes
contributes to deterioration
add directly to collection system
kills bacteria, removes early stages
TableS. Remedial Measures of Clogged Drains
Category Measure
effectiveness
Comments
Excavation and
Replacen.snt
Physical Methods
Chemical Methods
same
mechanical
low pressure jets
high pressure jets
flushing (sub-
irrigation
SOz gas
SuHamic Acid
complete remedy
limited for inactive deposits, not
effective for slots, but good in
combination with other methods
effective for ochre. FeS. sediments
limited for mature deposits
same as low pressure but can cause
damage to drain envelope and better
for mature deposits
less than jets
effective for ochre. Mn in 2 cases,
ineffective in one case for ochre
effective for ochre
most expensive option; difficult
at hazardous waste sites
Koto-rooter, pigs, sewer balls,
snakes, buckets
70-140 psi at nozzle
440 - 1300 psi at nozzle
rate of use = / lb/7.Sg water,
dangerous to personnel and
environment, cost is 7 percent
of replacement
strength required depends on
organic matter and age of ochre
NaCOa used to neutralize
treated live
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layers should be developed. Currently,
no satisfactory remedial methods exist
short of excavation and replacement.
6. Experimental data on the perform-
ance of leachate collection systems
(including detailed leachate flow
and composition data) should be
gathered at both sanitary and
hazardous waste landfills on a
continuing basis. Such a data base
is vital in evaluating leachate
collection system performance and
in developing design and operational
guides to ensure proper system
functioning throughout its required
lifetime.
The full report was submitted in
fulfillment of Contract No. 68-01 -5949
by Arthur D. Little, Inc., under the
sponsorship of the U.S. Environmental
Protection Agency.
Jeffrey M. Bass, John R. Ehrenfeld, and James N. Valentine are with Arthur D.
Little. Inc., Cambridge. MA 02140.
Michael Slimak is the EPA Project Officer (see below).
The complete report, entitled "Potential Clogging of Landfill Drainage Systems,"
(Order No. PB 84-110 550; Cost: $10.00. subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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United States
Environmental Protection
Agency
Official Business
Penalty for Private Use $300
Center for Environmental Research
Information
Cincinnati OH 45268
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U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/853
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