United States
                    Environmental Protection
                    Agency
Municipal Environmental
Research Laboratory
Cincinnati OH 45268
                    Research and Development
EPA-600/S2-84-092 Sept. 1984
v>ERA          Project  Summary
                    Production  and Management  of
                    Leachate from  Municipal
                    Landfills:  Summary and
                    Assessment

                    James C.S. Lu, Bert Eichenberger, Robert J. Stearns, and Ihor Melnyk
                      Production  and  management of
                    leachate from municipal landfills were
                    evaluated to identify practical informa-
                    tion and useful techniques for design
                    engineers  and  site operators. Advan-
                    tages, limitations,  and comparative
                    costs were also assessed for various
                    approaches to the problem. The study
                    addressed public health impacts, man-
                    agement options, and additional research
                    needs on the generation, control, and
                    monitoring of landfill eration, contol, and
                    monitoring of  landfill leachates. Nu-
                    merous mathematical models have
                    been proposed for estimating leachate
                    generation, and they are usually based
                    on the water balance method. Several
                    fairly successful models are proposed
                    here for simulating the change in
                    leachate strength with  increasing
                    landfill age of cumulative leachate
                    volume. A program to monitor the zone
                    of saturation is established  to give a
                    prompt indication of groundwater
                    contamination.
                      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
                     In 1990, a projected 295 to 341 million
                    metric tons of municipal refuse will be
                    produced  in the United States. When
                    water passes through this refuse in a
sanitary landfill, it accumulates various
contaminants. This percolate or leachate
may then enter underlying groundwaters
and seriously degrade the water quality
of the aquifer. Landfill leachate may thus
exert a major environmental impact.
  Leachate production can be minimized
or nearly eliminated by preventing water
contact with the refuse by the use of
surface and subsurface drainage and
properly selected cover material that is
graded and seeded with a high evapotran-
spiration (ET) crop. Various  studies
concerning  sanitary landfill behavior
have been conducted to understand,
delineate, and define significant manage-
ment options.
  The objectives of this study were: (1) to
clarify the understanding of leachate
production and management  options
through a critical review and analysis of
existing  information; (2) to identify
practical information and techniques that
can be used by design engineers and site
operators; (3) to delineate weaknesses in
the available data base; and (4) to identify
useful techniques  for estimating and
mitigating the environmental and public
health impacts of leachate generation.
The specific objectives were to document:
(1) current methods, advantages, and
limitations of various approaches; (2)
comparative costs; (3) additional research
needs on  the generation, significances,
and associated costs of controlling and
monitoring  leachate from municipal
landfills. Presentation of the results is in
terms of leachate generation, composition,
and migration, available control technol-
ogy, and environmental monitoring.

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Leachate Generation

  Leachate generation at a landfill site
depends on  many factors.  Volume is
generally determined by the availability of
water, landfill surface conditions, refuse
conditions, and underlying soil conditions.
Factors affecting  availability of water
include direct precipitation, surface run-
on, groundwater  intrusion, irrigation,
refuse decomposition, and co-disposal of
liquid waste  or  sludge with refuse.  In
most cases, precipitation  (including
rainfall and snowfall) will be the principal
source  of leachate. Many methods for
estimating  leachate generation neglect
the effects of rainfall intensity, frequency,
or  duration.  Intensity influences the
impact of raindrops on the surface soil
particles, which could change infiltration
rates and leachate quantity. Frequency
and duration  also  affect infiltration and
runoff. Quantitative information on  the
effects of such rainfall characteristics on
leachate generation is lacking. Snowmelt
usually occurs  at rates  considerably
below the infiltration capacity of unpacked
soils. Surface runoff from snowmelt may
therefore be rare.
  Surface run-on is mostly affected by
surface topography and can be determined
by  surface measurement, empirical
formulas,  or graphic methods.  The
rational method is expressed in terms of
uniform rate of rainfall intensity, landfill
area,  and a runoff coefficient. The key to
successful  estimation of  surface runoff
by  the  rational  method  is the correct
choice of the coefficient  dependent on
surface characteristics, type  and extent
of vegetation, and  surface slope. Cook's
method uses an empirical  relationship
between drainage  area and peak flow,
with  modifications for climate, relief,
infiltration, vegetal cover, and surface
storage. Other methods include the
Burkli-Ziegler and McMath formulas.
Groundwater intrusion  occurs  if the
base  of the landfill is below the ground-
water table. This condition may be
determined by a hydrologic investigation
and calculations  using  Darcy's Law.
Precise measurement of underground
flow  is not  feasible. The extent  of
microbial activity and consequent water
production depends mainly on the amount
and pH of interstitial moisture,  tempera-
ture,  presence of  oxygen,  composition
and particle size of the refuse, organisms
present,  and the degree  of mixing.
Decomposition  is much faster under
aerobic than anaerobic conditions. Under
aerobic conditions, decomposition may
reduce volatile matter and carbon con-
centrations by 50% in a year.
  The  volume  of  water available for
leaching from disposal of sewage sludge
with municipal solid waste may be
affected  by the type  and amount  of
sludge, moisture  content, moisture-
holding  capacity,  and the  effect  of
compaction and decomposition of the
release of water. ET, which is the sum of
water loss by evaporation and transpira-
tion, is affected by vegetation and cover
material  (type,  dimension,  compaction,
etc.), surface topography,  temperature,
humidity, and  wind speed above the
landfill. ET determination  methods fall
into three general categories—theoretical,
analytical, and  empirical. Various mea-
surement  methods are soil-moisture
sampling, lysimeter measurements, and
adjusted pan evaporation. Many empirical
or theoretical equations have been
derived for estimating ET  rates.  Some
typical  equations are the Hedke, Lowry-
Johnson, Blaney-Morin, Blaney-Criddle,
Thornwaite, and  Penman equations.
Leachate may be channeled through the
refuse and dispersed  by  intermediate
cover layers, or it may seep through the
pores of the refuse. If no channeling has
occurred in the refuse, leachate will first
appear when soil cover and refuse reach
field capacity. The  time  required for the
first appearance  of  leachate  can  be
obtained using the moisture-routing
calculation or by using a graphic technique.
If channeling does occur,  leachate will
not be  produced until at least a portion of
the refuse reaches field capacity. Specific
information describing the  effects  of
management or operating  practices  on
leachate  production is not available.
  Numerous  mathematical methods
have been used for quantitative estimates
of the volume of leachate generated from
landfills.  The approaches are all derived
from the water balance principle—a one-
dimensional flow model based upon the
retention and transmission characteristics
of the refuse and cover soil. Although the
water  balance method has been widely
used for estimating landfill leachate, the
accuracy and sensitivity of the method for
the actual landfill are less studied. More
than a hundred different approaches are
available for water balance calculations,
but no comparisons have been  made to
identify  which approach can  achieve
better  results,  or which is suitable  for
what types of landfill  conditions. The
applicability and accuracy of the water
balance calculations can be determined
by analyzing the suitability of the approaches
and the closeness of the  calculated
results to  actual  measurements. Site
verification of various  leachate estima-
tion techniques is largely lacking, however.
Applicability and accuracy are difficult to
verify for actual landfills because of the
lack of accurate leachate generation data.
Selection of applicable leachate volume
estimation methods should thus be based
on the specific site circumstances,
availability of data, scientific and engin-
eering judgments, and the experience of
the designer and  operator  in leachate
generation estimation.
   Numerous methods have been proposed
for determining infiltration capacity and
rate. Theoretical methods are not recom-
mended because of their highly simplified
nature and their requirement  for deter-
mining  special watershed  properties.
Three general  appoaches  are: actual
measurement, estimation from runoff,
and empirical calculation. The American
Society of Civil  Engineers (ASCE) empiri-
cal method is based on relative minimum
infiltration  capacities and  takes  into
account vegetal covers.  Equations  also
exist for snowmelt infiltration.


Leachate Composition
  Leachates are usually highly contam-
inated and can degrade  surface water
and groundwater. Viruses are  only
occasionally detected in  leachates,
though  their  potential  presence in
leachates of fresh refuse  cannot  be
overlooked. Bacterial and viral  populations
decrease significantly  with refuse age or
time of leaching. Elevated landfill temper-
atures resulting from biodegradation can
help to  inactivate bacteria and destroy
viruses.  The chemical characteristics of
leachate also  contribute to  bacterial
inactivation. Little work has been done
regarding fungi  and parasites in leachate.
  The rate of solubilization of a refuse
mass is governed by  specific  microbial
populations dependent on chemical  and
physical processes, including pH effects,
redox effects, precipitation, ion exchange,
adsorption  and complexation,  biological
effects,  physical sorption effects,  and
temperature.  These processes create a
highly complex  and dynamic  system and
considerable  variability in  leachate
composition.
   Leachate composition is a function of
numerous factors, including those inher-
ent  in the refuse mass and landfill
location, and those created by designers
and site operators.  The chemical  and
microbiological character of  refuse is
largely uncontrollable. Ambient tempera-
tures and rainfall are unalterable charac-
teristics, but refuse density, permeability,
depth, and water  application can be
regulated.  Compared with unshredded
refuse, shredded material yields increased

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landfill field capacity, a greater concen-
tration of pollutants in leachate, and a
higher rate of pollutant removal per
volume of leachate. Conversely, baling
produces a more dilute leachate, delays
attainment of landfill field capacity, and
removes less mass per volume of leachate
than shredded or unbaled refuse. Higher
rates of water application produce more
dilute leachate and greater mass removals
as a function of time. Increasing landfill
depth promotes stronger leachate. Land-
fill  temperature fluctuates with the
seasonal  ambient temperature variation
near the landfill  surface, but these
amplitudes  are less pronounced with
increased landfill depth.
  The addition of municipal wastewater
treatment plant (WWTP) sludges or
industrial  sludges to municipal  landfills
provides  both beneficial  and adverse
effects on leachates. WWTP sludge and
refuse  admixtures accelerate the rate of
stabilization of biodegradable  organic
matter. The addition of industrial waste
may cause more toxic elements to occur
in leachates and may adversely affect the
biochemical stabilization processes.
Some  of  the  specific findings  are as
follows:
  1. Seeding municipal refuse with
     primary sewage  sludge increases
     the  biological stabilization  rates of
     organic pollutants.
  2. Addition  of septic  tank pumpings
     accelerates the methanogenic pro-
     cess.
  3. Bacterial loading does not increase.
  4. Leachate organics and total dissolved
     solids (TOS) are reduced.
  5. Inorganic ion concentrations are
     largely unaffected.
  6. Admixed WWTP sludge and refuse
     produces an acidic  leachate with a
     higher  BOD, but chemical composi-
     tion does not differ.
  7. Co-disposal  accelerates leachate
     formation through the  additional
     moisture.
  8. Epidemiological evidence of diseases
     resulting from WWTP  sludge co-
     disposal is lacking.
  The  leaching  trends of chemically
stabilized and unstabilized  industrial
wastes disposed with municipal solid
waste (MSW) are as follows:
  1. The release of major metal contami-
     nants from treated  or  untreated
     electroplating sludge was  not ob-
     served  when it was disposed with
     MSW.
  2. Untreated chlorine production brine
     sludge disposed with MSW releases
     significant quantities of aluminum.
     cadmium, copper, chJorine, mercury,
     sodium, and other dissolved solids.
  3. Disposal of  MSW with chemically
     stabilized chlorine production brine
     sludge  significantly reduces  the
     mass release of toxic metals.
  4. Disposal of MSW with calcium
     fluoride and sewage sludge improves
     leachate quality  with respect to
     BOD, COD, TOC, alkalinity, pH,  and
     iron.
  Two approaches can be used to model
the  composition of leachates as  a
function of time or cumulative leachate
volume: (1) to describe quantitatively the
physical,  chemical, and  biological  pro-
cesses that occur during leaching, and (2)
to avoid  mathematical  expression  and
focus on leachate concentration histories.
The models are sensitive to such factors
as refuse placement and composition,
hydraulic  phenomena, and landfill con-
figuration. Agreement of the various
models with experimental data  ranges
from fair to very good. At  present,
leachate composition models are appro-
priate primarily  for research purposes,
since as mathematical expressions they
merely interpret experimental results.

Leachate Migration
  Soils  are  chemically  sorbent  bodies
consisting of: (1) inert chemical compounds,
(2) difficult and easily soluble substances,
(3) soluble salts and acids, (4) complex
insoluble  compounds, and  (5) a wide
variety of organisms.  Soil represents a
medium in which a series of complex
biological  activities are occurring simul-
taneously. Soil properties most useful in
predicting the  mobility of leachate
contaminants are: (1) texture, (2) content
of hydrous oxides, (3) type of content of
organic matter, (4) particle size distribu-
tion, (5) cation exchange capacity, and (6)
pH.  The attenuation  and migration of
contaminants  in the soil and water
system are influenced by diffusion  and
dispersion, dilution, straining, precipita-
tion/dissolution, adsorption/desorption,
complexation, ion exchange, redox,  and
microbial activity.
  The most important physical properties
relative to leachate migration are diffusion
and dispersion,  dilution, sorption,  and
straining. Hydrodynamic dispersion is the
result  of  variations in pore velocities
within a soil. It is effective in attenuating
the  maximum constituent concentration
rather than the  total quantity  of  the
constituent in a pulse or slug of leachate.
Complexation  involves the reaction of
metal ions with  inorganic anions  and
organic  liquids.  Complex  formation
 affects attenuation and migration in two
 ways: In solution, it greatly increases the
 concentration of constituents by forming
 soluble complexes;  or, if the complex
 formation exists between the soluble
 constituents and solid surfaces, the
 constituents  levels decrease. Most ion
 exchange effects orginate from exchange
 sites on layered silicate clays and organic
 matter. The exchange capacity of soils is
 affected by the kind of quantity of clay
 mineral and organic matter and the pH of
 the soil/water solution. Redox reactions
 occur when redox potential in leachates
 is different from that  of  soil solutions.
 Redox reactions are greatly affected by
 degradation of organic compounds in the
 soil. Through biological assimilation, the
 trace metals  may be  transformed into
 microbial tissue  and immobilized. The
 migration of trace metals in the soil/water
 system is extremely complex. The fate of
 chlorinated hydrocarbons, is very difficult
 to predict. Volatilization,  microbial de-
 gradation, chemical hydrolysis, oxidation,
 and sorption  can be involved. The fate of
 pesticides in soil/water systems involves
 adsorption/desorption, microbial decom-
 position, volatilization, soil moisture, and
 physical properties of the soil. Adsorption
 /desorption is considered most important.
 Virus survival depends on soil  moisture
 content, temperature, pH, nutrient avail-
 ability,  and  antagonisms. Viruses that
 penetrate the soil surface are expected to
 survive longer than those retained near
 the surface.
  Leachate migration models can  be
 classified into four generic categories:
 descriptive, physical,  analog, and mathe-
 matical models. The  models  can also be
 subcategorized by method of analysis and
 particular approach. Empirical models
 are  based completely on observation
 and/or experimentation. Conceptual
 models use equations based on conser-
 vation of mass, energy, and momentum.
 In a deterministic model, all input
 variables and system parameters are
 assumed to  have fixed mathematical
 relationship with each other. Stochastic
 models take  into account intrinsic ran-
 domness associated with parameters.
 Static models evaluate steady-state
 conditions, and dynamic models evaluate
 changing variables.  One-,  two-,  and
 three-dimensional models may also be
 used.

Available Control Technology
  Environmental  control  technologies
are divided into four areas: Groundwater
control, leachate composition control,
collection systems, and treatment methods.

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  Groundwater control measures are
presented in terms of groundwater/leach-
ate isolation and leachate plume control.
The  groundwater/leachate isolation
methods can be defined as those approaches
by which  contaminants are contained
within the fill and  not permitted to
migrate  into the groundwater.  The
available  control techniques include
synthetic liners, bottom sealers, slurry
trenches, grout curtains, and sheet piling
cutoff walls. The liners may be used both
as collection  devices and as means for
isolating leachate. Bottom sealing offers
advantanges,  especially in coarse soils
and  gravels. The  seal can  prevent
groundwater  from entering the fill and
impound the  leachates formed. A slurry
trench prevents the horizontal subsurface
movement of water.  Its advantages
include simple construction methods,
leachate-resistant bentonites, low main-
tenance, and  minimal liner deterioration.
Slurry trenches are most effective where
a shallow groundwater condition exists
and an impermeable  bedrock stratum is
available for  contact with the barrier. A
grout curtain  performs a function similar
to that of a slurry trench. Advantages of
sheet  piling  cutoff  walls  over  slurry
trenches and  grout curtains are ease of
construction,  maintenence-free nature,
and low construction costs.
  Plume control refers to efforts to isolate
a contaminated groundwater body.
Methods involve drains to intercept up-
gradient groundwater to lower the water
table,  well point systems  to prevent
groundwater flow through the fill  or
leachate collection down gradient, and
deep-well systems that  are a deeper form
of the well point systems. Surface water
control measures such as contour grading,
surface water diversion, surface sealing,
and  revegetation  are used  to  minimize
the quantity of water entering the landfill.
  The purpose  of leachate  composition
control  is  to reduce the strength and
contaminant  flux  of  leachate.  Leachate
recirculation  offers advantages such as
accelerated  refuse  stabilization, and
treatment systems are not always required.
Co-disposal of sewage sludge or alkaline
wastes can help to accelerate stabilization.
The  use of limestone  as  an additional
attenuation layer is an effective, low-cost
aid in controlling  the migration of heavy
metals.
  The approaches to leachate treatment
are biological (aerobic and anaerobic)and
physical/chemical (precipitation, adsorp-
tion, coagulation,  oxidation, and reverse
osmosis). Newly formed landfill leachate
is best treated by biological processes,
whereas leachate from stabilized landfills
is  best  treated with physical/chemical
methods. Aerobic treatment can effec-
tively remove organic matter and metals
from leachate. Removal of 90% to 99% of
BOD and COD and some metal removal
have commonly been reported. Problems
with aerobic treatment include long
treatment times, foaming, nutrient defi-
ciencies, toxic inhibition,  and  oxygen
depletion. Anaerobic treatment has been
effective in  reducing organic loads:
Organic removals of 90% to  99% have
been  demonstrated. Advantages over
aerobic treatment are low solids buildups
and an absence of aeration requirements,
which allows energy savings. Treatment
times are comparable. A major product of
anaerobic digestion is  methane, which
can be used as an energy source.
  The  successful  treatment of high-
strength leachates requires combinations
of biological and physical/chemical pro-
cesses. The design of a treatment system
depends not  only a leachate  character,
but on location. Landfills near a wastewa-
ter treatment plant may take  advantage of
the facility, but distance sites will require
an aerated lagoon,  land application, or a
complete treatment system. Treatment
costs may represent 25% or  more of total
landfill costs.
Environmental  Monitoring
  The  zone of aeration  is that area
beneath the top soil and  overlying the
water table in which pore space co-exists
with air, or  in which  the geologic
materials  are  unsaturated.  Monitoring
the zone of aeration may be achieved with
or without sampling. Sampling approaches
include pore water extraction from soil
cores and deployment of pressure/vacuum
lysimetersto obtain in situ water samples.
The water samples may  be analyzed for
major  anions,  trace metals, TOC, pH,
specific conductance, organics, and other
specific  constituents.  Core samples
provide information on physical  charac-
teristics  such  as  soil  texture, water
content, hydraulic conductivity, and bulk
density. For shallow sampling of soils and
vadose waters, traditional hand augers
and bucket-type samplers  may be used.
For deeper sampling, standard drilling
equipment is required.
  Nonsampling approaches to monitoring
require tensiometers, psychrometers,
electrical resistance blocks, and  neutron
moisture logging. Nonsampling methods
provide for the determination of water
content and movement in  the vadose
zone.  Tensiometers  employ a mercury
manometer to  measure soil-water pres-
sures during unsaturated flow conditions.
Psychrometers use a porous bulb with a
chamber to measure relative humidity in
the soil.  Electrical resistance  blocks
measure either soil-water content or
pressure.  The  neutron thermalization
method measures changes in the volu-
metric water content within a soil horizon
and delineates perched water zones and
estimates flow rates.
  The zone of saturation is that portion of
the groundwater system in which avail-
able pore  space is  occupied by  water.
Monitoring within the  zone of aeration
has traditionally been accomplished with
single-screened  wells. But the  cluster
well and the air-lift sampler allow for
multiple sampling points throughout the
aquifer. Multi-sampling wells provide a
vertical distribution of contaminants and
greater flexibility, especially in  three-
dimensional volume monitoring.
  Selection of the optimum location for
sampling  and nonsampling devices is
largely site-specific.  In  all cases, the
devices are situated below the landfill to
maintain contact with interstitial waters.
  Monitoring frequency should be flexible,
allowing for modifications at each site.
  Monitoring parameters are determined
largely by the purpose of  the monitoring
program (Table 1). Many researchers
have developed lists  of  key indicator
parameters. Their selection should be
modified,   as  required,  to meet site-
specific situations.
  EPA and the  American  Public  Health
Association  (APHA) provide detailed
descriptions of appropriate containers for
various chemical species and sampling
techniques. Methods  are intended  to
retard biological activity, retard hydrolysis
of chemical compounds and complexes,
and reduce the volatility of constituents.
Preservation techniques are generally
limited to pH control, chemical addition,
refrigeration, and freezing.

Conclusions and
Recommendations
  The quantity of leachate produced from
a municipal landfill may vary considerably
with management or operating practices,
depending on whether leachate is viewed
as a short- or long-term problem. Opera-
tional  factors which  affect  leachate
quantity may include: cover material
handling, watering prior to compaction,
watering  following compaction, daily
variation in cell construction, and variation
in waste composition  (e.g., municipal
refuse  alone or codisposal of municipal
refuse  and sewage sludge or industrial
wastes; milled or unmilled refuse)
  Numerous mathematical  methods
have been proposed for  a quantitative

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 Table 1.    Monitoring Parameters and Applicable Situations
    Parameter
            Applicable situation
 Suitability of aquifer as a drinking water source
 Chlorine, iron, manganese, phenols, sodium, and sulfate
 Specific conductance, pH, total organic carbon, and
 total organic halogen
         Need exists to identify facilities that
         may be severely degrading present
         and future drinking water supplies.

         Groundwater contamination must
         be assessed after it is determined
         that a facility is leaking.

         A threshold assessment must be
         made as to whether a facility is leak-
         ing.
estimation of the volume of leachate
generated from landfills and are usually
based on a mass balance approach (i.e.,
water balance method). Components of'
these  models are relatively  easy to
obtain, but other model variables such as
the surface runoff coefficients, runoff
curve number, and evapotranspiration
from the landfill surface are more difficult
to develop. Limited field data exists for
verification  for  many of  the leachate
generation models. Therefore, the appli-
cability, accuracy, and sensitivity of
leachate generation models, is largely
unknown. Additional research should be
conducted regarding such variables  as
water contribution from refuse degrada-
tion, refuse permeability, evapotranspira-
tion, surface  runoff  coefficients, and
runoff curve numbers.
  The composition of leachate produced
from a  municipal landfill is highly
variable, depending on  factors  such  as
refuse  composition, refuse  processing,
landfill age, the rate of infiltration, landfill
depth,   and  landfill temperature. The
quality of leachate can be controlled to a
large degree.  Shredding and  baling of
refuse,  landfill depth,  and  the rate of
water application to the landfill surface
can influence the rate at which contami-
nants are released from refuse, and can
determine whether leachates have a
long- or short-term pollution potential.
  Based on empirical data garnered from
a number of studies addressing landfill
and  leaching  behavior, several models
have been developed which describe
leachate quality as a function of time or
cumulative  leachate generation. The
most promising of these models attempts
to simulate  the physical/chemical and
biological  processes which occur during
leaching. Presently, however, the leachate
composition models are useful only in in-
interpreting  experimental  results  rather
than in finding application  to  field-
scale problems.
  Leachate migration  models are  based
upon constituent mass transport and
water flow equations. Numerous models
are available for predicting chemical and
physical migration; biological models,
however, are generally lacking. While a
large number of conceptual-mathematical
models exist,  none  are universally
applicable  for  the simulation of all the
physical, chemical, and  biological  pro-
cesses  that are  operative in  a typical
waste disposal system. The complexity of
these  processes, which operate in a
simultaneous and interactive manner, is
probably such that the development of a
generic model would  be impractical
because the resulting program would
undoubtedly become so large and complex
that the cost  of  operating it would be
exorbitant.
  Leachate control  technology  is  a
relatively well-developed methodology
for the management of landfill leachates.
Various groundwater and surface water
control approaches  are available for the
control of leachate into or out of the fill.
Approaches in which  dewatering or
counter pumping (injection) is practiced
appear to be effective control measures,
although the long-term energy costs for
pumping are restrictive. Accelerated
stabilization processes such as leachate
recycling   and nutrient addition  are
promising,  but  require additional study.
Extensive  liner technology is available;
however, field verification studies have,
in general,  been  inconclusive regarding
anticipated  liner lifetime.
  Vadose zone  monitoring has received
little attention in contrast to the advanced
technology  for monitoring in the zone of
saturation.  This discrepancy reflects, to a
large extent, the greater complexity of
flow in the vadose zone, compared to
saturated flow, and the related problem of
obtaining  a representative sample for
analysis. Incorporation of vadose  zone
devices can provide an early warning of
potential groundwater pollution. If reme-
dial measures are implemented prior to
the onset of extensive groundwater con-
tamination, the associated renovation
costs could  be reduced significantly.
Additionally,  an effective vadose zone
monitoring  network  could reduce, or
largely  preclude, the requirements  for
groundwater monitoring. The savings in
costs for  construction  of groundwater
wells could be significant, particularly in
western regions where water tables are
often hundreds of feet deep. Vadose zone
monitoring requires additional  study to
better define both  the dominant pheno-
mena occurring in this zone, as well as
optimum monitoring equipment.
  The full  report was submitted in
fulfillment of Contract No. 68-03-2861 by
Calscience  Research, Inc., under the
sponsorship of the U.S. Environmental
Protection Agency.
*USGPO:  1984-759-102-10664

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      James C. S. Lu, Bert Eichenberger. and Robert J. Stearns are with Calscience
        Research, Inc., Huntington Beach, CA 92647; the EPA author. Ihor Melnyk, is
        with Municipal Environmental Research Laboratory, Cincinnati, OH 45268.
      Wendy J. Davis-Hoover is the EPA Project Officer (see below).
      The complete report, entitled "Production and Management of Leachate from
        Municipal Landfills: Summary and Assessment," (Order No. PB 84-187 913;
        Cost: $34.00, subject to change) will be available only from:
              National Technical Information Service
              5285 Port Royal Road
              Springfield. V'A 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
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
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