United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/017 July 1986
Project Summary
Leachate Collection and Gas
Migration and Emission Problems
at Landfills and Surface
Impoundments
Masood Ghassemi, Kimm Crawford, and Michael Haro
The available information on clogging
potential of landfill (LF) leachate col-
lection systems (LCS) and on gas migra-
tion and emissions at LFs and surface
impoundments (SI) was reviewed; as a
further step, corrective and preventive
measures and research and develop-
ment (R&D) needs were identified.
There has been limited operating ex-
perience with LCS and little opportunity
for corrective action at hazardous waste
landfills (HWLFs) that meet or exceed
RCRA design and operating standards.
Gas generation and migration problems
are largely associated with municipal
and co-disposal LFs. The limited avail-
able air emissions data indicate ambient
concentrations of specific pollutants
near the detection limits of the sampling
and analytical procedures used. LCS-
and gas-Xemissions-related problems
can best be addressed through preven-
tive design and operating measures.
Areas for R&D include development
of an improved basis for LCS design,
evaluation of innovative approaches to
LCS design, evaluation of cost-effective
methods for retrofitting older sites with
LCS, parametric evaluation of various
cover systems for LFs from the stand-
point of emissions control, and expan-
sion of the current data base on
emissions.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
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
A recent study of liner installation
practices and an assessment of surface
impoundment (SI) technology led to
identification of a number of design- and
operation-related problem areas requiring
further studies. Two such areas, which
are the focus of the present study, relate
to leachate collection systems (LCS) and
air emissions from landfills (LFs) and Sis.
Early review of the literature indicated
little information in the areas of interest.
Accordingly, the present study em-
phasized acquisition of information and
professional perspectives from design
engineers, owners and operators of land
disposal facilities, and cognizant state
regulatory agencies.
Problems With and Remedies
For LCS
Limited information is available on the
extent of LCS clogging in engineered
hazardous waste landfills (HWLFs). Most
of the reported LCS problems occur with
the older systems (primarily at municipal
or co-disposal sites), which lacked sophis-
ticated designs. LCS clogging was a
problem of major concern at only one site
studied in this survey — a unique co-
disposal facility handling a significant
volume of liquid industrial waste; two
HWLFs reported some previous experi-
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ence with minor siltation in the LCS
standpipes. Corrective actions taken at
some co-disposal sites include (a) using
gravel trenches or pipes to intercept
leachate, (b) installing caissons in LFs
and pumping out the accumulated leach-
ate, and (c) replacing sections of the
collection system where the depth of the
overlying waste is not significant. Such
corrective actions, however, would be
very costly, especially for large HWLFs
and can present considerable risk and
safety hazards. Accordingly, the problems
can best be addressed through preventive
means involving a combination of good
design, construction and operating prac-
tices. Some helpful considerations are
listed in Table 1. These are aimed at
reducing the potential for leachate
generation, providing better leachate
control, and reducing adverse impacts on
LCS.
Gas Migration and Air Emission
Problems and Applicable Controls
The very limited attempts at systematic
evaluation of emissions from HWLFs have
been largely of a problem-definition
nature with a major objective of develoing
suitable sampling and analytical protocols.
These studies have yielded variable re-
sults apparently caused by (a) emission
contributions from other sources, (b)
activities at the disposal sites tested, and
(c) the yet unproven reliability and ac-
curacy of the sampling and analysis
protocols used. As these studies indicate,
volatile organics are difficult to measure
at closed HWLFs because the ambient
concentrations of specific compounds are
often near or below the detection limits
of the methods employed.
LF gas characterization established
from samples collected at municipal and
co-disposal LFs indicate that (a) ppm
levels of chlorinated and/or aromatic
hydrocarbons are present in gas from all
LFs; (b) the levels of these gases (which
include some hazardous compounds such
as benzene) are not necessarily higher in
sites that have accepted hazardous
wastes; and (c) the volatile organic
compounds (VOC) content of the gas
varies greatly, both among the LFs and
within an LF Unless an LF is equipped
with an effective gas extraction system,
the gas produced would be gradually
emitted to the atmosphere; such LFs
should therefore be regarded as point
sources of air pollution.
Since there should be little biological
activity in a properly operated HWLF,
emissions from a closed HWLF would
involve primarily waste volatilization.
Preventive measures would include (a)
use of multiple cell design to segregate
wastes; (b) use of state-of-the-art liners
and covers (c) control of vents, sumps,
cleanouts, etc.; (d) source control; (e)
placement of waste to prevent formation
of internal barriers to gas flow; (f) control
Table 1. Key Considerations For Improving Site Performance From The
Standpoint of Leachate Management
Consideration
Objective/Description
Progressive Design
Infiltration Control
Segreated Waste Disposal
Ease of Access
Covers for Manholes
Traffic on Pipes
Leachate Head Control
Side Slopes
Construction QA/QC
Course Control and
Waste Placement
Preventive Maintenance
Limiting the size of the active cell, thereby restricting the leachate
volume to water emering cell during short active life
Using state-of-the-art cover design and surface and subsurface
water interception systems
Dedicating specific cell/areas to specific waste/waste type and
tailoring design and operation to specific waste properties
Providing easy access to pipes for inspection and maintenance
through the use of specialty pipe connectors, sweep bends, 6-in. or
larger pipes, cleanouts at strategic locations, etc.
Preventing wind-blown debris from entering lines
Minimizing potential for pipe collapse through design/operation
which would eliminate or reduce traffic on pipes
Using level-activated leachate pumping system with high level
alarm and leachate head observation wells in the fill
Using suitable side slopes and protective cover to prevent erosion
washing of clay from side slopes
Supervising construction to ensure conformance with design specs.
Not accepting liquids, placing sludges and low permeability wastes
near top, using permeable material as intermediate cover, etc.
Periodically inspecting and cleaning lines and cover maintenances
of runoff; and (g) control of fugitive emis-
sions from waste handling and placement
activities.
At municipal and co-disposal LFs, emis-
sion control measures include source and
operating controls, venting, interception
and collection of gas for incineration or
energy recovery. Source controls involve
(a) excluding disposal of bulk solvents
and wastes containing a high concentra-
tion of volatiles, and (b) neutralization/
inactivation of certain troublesome
wastes (e.g., via solidification) prior to
disposal. To prevent lateral migration of
gas to nearby structures and to facilitate
gas collection for energy recovery, operat-
ing controls are aimed at eliminating
internal barriers to gas movement. The
systems employed at a number of sites
for interception and collection of LF gas
fall into two categories, passive and active.
The passive systems are aimed at re-
leasing the internal gas pressure in the
LF by providing wells and trenches in or
around LFs for venting of the gas to the
atmosphere. Passive systems would not
provide acceptable emission control, since
any toxic substances in the gas would be
released to the atmosphere. Active gas
systems use blowers to collect gas
through a network of extraction wells
and/or trenches. The collected gas is
either disposed of by flaring or combusted
for energy recovery. In either case, a high
degree of destruction of toxic organics
can be achieved when combustion
temperatures are kept at 800°C or
greater.
Currently, very little quantitative data
exist on volatile toxic emissions from Sis.
Much of the concern over SI emissions
has involved odor complaints. The most
common solutions for such problems have
been source control and proper siting.
Most SI emissions studies have in-
volved comparative testing of various
sampling protocols and equipment and
verification of predictive models. Results
from the limited number of Sis tested
indicate very low VOC emissions (often
near the detection limits). Agreement
between the results using different
sampling protocols and between the mea-
sured values and those predicted using
models is currently not complete.
Emission controls for Sis include source
control, proper siting and use of side
enclosures, floating covers, surface films
and wind fences. Source control, con-
sidered by some to be the most viable,
involves reducing the concentration of
volatiles in the raw waste stream or the
potential for their emission through in-
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plant controls or wastewater pretreat-
ment. The applicability and effectiveness
of floating covers, surface films, wind
fences, etc. are very waste- and site-
specific. Some of these measures would
most likely be inapplicable to (or not
economical for) very large impoundments
or where Sis are to serve as evaporation
disposal ponds. Also, at present there is
very little experience with the use of
these systems in full-scale facilities.
Moreover, unless the volatile constituents
in the wastewaters are biodegraded or
modified, or collected and destroyed (e.g.,
via incineration of overhead vapors), the
emissions control for Sis may only serve
a temporary purpose and the problem
would be accumulated or transferred to
downstream treatment systems.
Recommendations
Areas suggested for further R&D
include:
• Studies of LCS performance in full-
scale facilities.
• Evaluation of cost-effective approaches
to retrofitting older sites with LCS.
• Development of reliable systems for
monitoring the functioning of LCS.
• Evaluation of innovative design con-
cepts for LCS.
• Expansion of the data base for emis-
sions from HWLFs and Sis.
• Evaluation of various cover systems at
operating landfills from the standpoint
of emissions control.
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Masood Ghassemi, Kimm Crawford, and Michael Haro are with MEESA, San
Pedro. CA 90732.
B. Vincent Salotto andNorma M. Lewis are the EPA Project Officers (see below).
The complete report, entitled "Leachate Collection and Gas Migration and
Emission Problems at Landfills and Surface Impoundments," (Order No. PB
86-162 104/AS; Cost: $22.95, 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:
Hazardous Waste Engineering Research 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
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-86/017
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