United States
Environmental Protection
Agency
Municipal Environmental Research EPA-500/2-78-142
Laboratory August 1978
Cincinnati OH 45268
Research and Development
Guidance Manual
for Minimizing Pollution
from Waste Disposal
Sites
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EPA-600/2-78-142
August 1978
GUIDANCE MANUAL
FOR MINIMIZING POLLUTION FROM
WASTE DISPOSAL SITES
by
Andrews L. Tolman
Antonio P. Ballestero, Jr.
William W. Beck, Jr.
Grover H. Emrich
A. W. Martin Associates, Inc.
King of Prussia, Pennsylvania 19406
Contract No. 68-03-2519
Project Officer
Donald E. Sanning
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
11
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FOREWORD
The Environmental Protection Agency was created because of
increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony to
the deterioration of our natural environment. The complexity of
that environment and the interplay between its components require
a concentrated and integrated attack on the problem.
Research and development is that necessary first step in
problem solution and it involves defining the problem, measuring
its impact, and searching for solutions. The Municipal Environ-
mental Research Laboratory develops new and improved technology
and systems for the prevention, treatment, and management of
wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and
treatment of public drinking water supplies, and to minimize the
adverse economic, social, health, and aesthetic effects of pollu-
tion. This publication is one of the products of that research;
a most vital communications link between the researcher and the
user community.
This manual is intended as a general guide for municipal
officials faced with closing or neutralizing solid waste disposal
sites. It presents an overview of standard engineering practices
that can be applied to minimize pollution from inactive waste
disposal sites.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
111
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PREFACE
Most of the municipal refuse in. the United States is dis-
posed of in approximately 15,000 sites, two-thirds of which are
•••pen dumps. The Solid Waste Disposal Act as amended by the
Resource Conservation and Recovery Act (RCRA) of 1976 requires
die phasing out of open dumps within the next 5 years. With
the implementation of RCRA and more stringent State solid waste
disposal practices it is anticipated that the majority of the
approximately 10,000 open dumps will be closed within the next
L years and increased volumes of solid waste will be disposed of
in existing permitted sanitary landfills.
Closing open dumps and upgrading existing landfills both
involve minimizing or eliminating the potential for resource
•.:on Lamination, or "neutralizing" the waste disposal site. Neu-
tralization measures are used to reduce the amount or concen-
tration of the contaminants produced and/or to prevent or re-
direct their movement from the disposal site.
This manual has been prepared to introduce municipal offi-
cials to the subject of neutralizing existing and abandoned
v,aste disposal sites. Well known engineering practices which
have not been extensively applied to the solid waste field can
be used for site neutralization. Various methods for preventing
environmental degradation and estimates of their costs are pre-
sented herein.
This guide is not intended as a design manual. The plans
?.nd specifications for application of any method presented must
be designed by competent professionals on a site-specific basis.
Actual cost estimates for use of these methods will also have to
ne developed on the basis of current labor and construction costs
in the specific area being considered. The procedures and esti-
mates included in this manual are generalized. Therefore, for
neutralization of some waste disposal sites the methods may be
suitable, while for other sites, because of their size or spe-
cific characteristics, these methods may be impractical.
This manual represents one phase of a multiphase project
;:eiucj conducted under U.S. EPA Contract No. 68-03-2519 by A. W.
Martin Associates, Inc. Other phases involve the selection of an
abandoned waste disposal site for study, the design and implemen-
tation of remedial neutralization procedures, and the implementa-
r.ion of a monitoring program to determine the effectiveness of
c:':n- p r "> c e d u r e s .
iv
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ABSTRACT
The purpose of this manual is to provide guidance for rmnic-
loai officials and engineers in the selection of available engi-,
r.eering technology to reduce or eliminate leachate generation at
existing dumps and landfills. The manual emphasizes remedial
measures for use during or after closure of landfills and dumps
which do riot meet current environmental standards. All of these
measures must be designed and engineered by competent profession-
als for each specific site. Some of these measures are passive,
that is, they require little or no maintenance once emplaced.
Others are active and require a continuing input of manpower or
electricity. Since the emphasis of this manual is on techniques
of reducing leachate generation or controlling its movement,
V'sachate treatment processes per se are not detailed.
Most of the techniques, discussed herein deal with the
reduction or elimination of infiltration into landfills in one of
.j.ve categories: surface water control, passive groundwater
management, active groundwater or plume management, chemical
immobilization of wastes, and excavation and reburial. The
•lechnology presented is widely used in construction but has nor
ri'jcessarily as yet been applied to landfill closure.
Surface water control measures include contour grading,
surface sealing, and revegetating the landfill. These methods
.-reduce infiltration of precipitation through the landfill sur-
face, involve standard engineering procedures, and provide a
no cms of. finishing the site.
Passive groundwater control techniques are used to minimize
infiltration of groundwater into the fill. They involve more
technically advanced engineering procedures designed to provide
-IP. underground barrier between the groundwater and the landfill.
They are generally more costly and are useful for isolating a
Landfill when applied in conjunction with surface sealing meth-
oc:s.
Plume management procedures involve actively altering the
•jcurse of leachate movement by either adding or removing water
I'rom around the landfill. These methods can effect greater
oranges in water table elevations than can passive barriers but
require continued maintenance and energy supplies and are there-
Tore more costly.
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Chemical immobilization techniques include (1) the appli-
cation of chemically stabilized materials to the landfill as a
surface seal and (2) the injection of chemicals into the landfill
to destroy a potential contaminant. Only the first of these is
recommended as feasible for in situ landfill neutralization.
Chemical injection involves fairly sophisticated and expensive
technology.
Excavation and reburial of a landfill entails removing the
fill material from its present location and reburying it in an
engineered and environmentally sound landfill. The procedure is
effective but costly and technically difficult. It would be
recommended only for a severe pollution problem.
This report was submitted in partial fulfillment of Contract
No. 68-03-2519 by A. W. Martin Associates, Inc. under the spon-
sorship of the U.S. Environmental Protection Agency. This report
covers a period from February 1977 to September 1977, and work
was completed as of March 1978.
VI
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CONTENTS.
Foreword . • iii
Preface iv
Abstract v
Figures viii
Tables ix
1. Introduction. 1
2. Surface Water Control 5
Contour grading and surface water diversion. . . 5
Surface sealing 9
Revegetation 15
3. Groundwater Control 20
Bentonite slurry-trench cutoff wall 21
Grout curtain 25
Sheet piling cutoff wall 32
Bottom sealing 35
4. Plume Management • . . 39
Extraction 39
Injection. 47
Leachate handling 48
5. Chemical Immobilization 52
Chemical fixation 52
Chemical injection 56
6. Excavation and Reburial 62
7. Summary 65
Surface water control 65
Groundwater control 67
Plume management 68
Chemical immobilization 70
Excavation and reburial 70
References 72
Appendix
Unit Costs Used as Basis for Cost Estimates 78
VII
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FIGURES
Number Page
1 Generalized cross section of hypothetical landfill
case 2
2 Cross section showing water flow into and away
• from hypothetical landfill 3
3 Cross section of landfill showing contour grading
and surface water diversion 6
4 Cross section of capped landfill 10
5 Plan view of semicircular slurry-trench cutoff wall
around upgradient end of landfill 21
6 Cross section of landfill before and after slurry-
trench cutoff wall installation 22
7 Cross section of grout curtain at landfill 2^
8 Soil limits of grout injectability ..." 27
9 Typical two-row grid pattern for grout curtain . . . . 2?
10 Semicircular grout curtain around upgradient end
of landfill 30
11 Cross section of sheet piling cutoff wall at
landfill 34
12 Cross section of grouted bottom seal beneath
landfill 36
13 Cross section of drain downgradient from the
landfill 41
14 Plan view of well points or extraction wells used
to lower the water table upgradient from the
landfill 42
15 Cross section of extraction well at landfill 44
16 Cross section of landfill sealed with stabilized
waste material ^4
17 Pollution plume created by cyanide salts located
in the middle of hypothetical landfill 58
18 Cross section of landfill treated by chemical
injection 60
Vlll
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TABLES
Number Page
1 Relative Costs of Grout 31
2 Present Worth of Leachate Recycling Systems 51
3 Requirements for Chemical Treatment.of Cyanide
Pollution at Hypothetical Landfill 59
4 Summary of Estimated Costs and Characteristics
of Remedial Methods 66
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SECTION 1
INTRODUCTION
To ensure comparable cost estimates for the neutralization
methods presented in this manual, a hypothetical landfill site
was developed (see Figure 1). The standard unit costs used in
estimating are included in the Appendix. The assumed hypotheti-
cal site is a 4-hectare (10-acre) landfill located in the north-
eastern United States in a depression situated on a slope between
an upland groundwater recharge area and a groundwater discharge
area with a stream. The landfill is underlain by 30 m (100 ft)
of unconsolidated, fairly permeable materials of either glacial,
coastal, or saprolitic origin, underlain by an indeterminate
bedrock. The water table is 6m (20 ft) bej.ow the ground surface
and the lower 3 to 5 m (10 to 15 ft) of the landfill is in the
groundwater.
The landfill originated as a pushover burning dump. The
waste is 12 to 15 m (40 to 50 ft) deep and extends 3 to 5 m (10
to 15 ft) above the ground surface. The bottom 3 to 5 m (10 to
15 ft) was dumped rather than landfilled and is located below the
water table. The remaining waste was landfilled and covered with
very sandy material. Mainly municipal refuse has been accepted
at the site. However, during the time it was operated as a dump,
no records of the materials deposited were kept, and it is possi-
ble that several nearby industries may have dumped industrial
and/or hazardous wastes into the landfill.
A source of pollution from a municipal landfill is leachate,
which is an odorous, colored substance generated when water comes
into contact with municipal refuse. Leachate is generally of
high ionic strength and variable pH and may contain metallic ions
or organic compounds in toxic concentrations. Although some
leachate is generated during the initial compaction, settlement,
and stabilization of the refuse, the majority is produced by
water moving through the landfill. Water can enter a landfill
through the top or upgradient side, and leave as leachate through
the bottom or the toe (see Figure 2). As it moves through the
fill the water leaches soluble ions and organic compounds from
the waste and creates leachate. The leachate then percolates
down through the fill and either seeps out the toe of the land-
fill and contaminates surface waters, or enters the groundwater
which in turn may carry it to surface waters.
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4 hectares ( 10 acres)
3Om •
(lOOft
/V ' '••' -1 ' X'- /^
Q. • -.;: • .0. •-•
UNCONSOLl DATED
.EARTH MATERIALS. °-
Stream
/ -•-/ .
. ' ' • ;
BEDROCK
A'o/ /» Scale
Figure 1. Generalized cross section of hypothetical landfill case.
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UNCONSOLIDATED
EARTH MATERIALS
KEY
A - Infiltration through uncovered
refuse or cover material
B - Refuse containing leachable ions
and organic substances that pro-
duce contamination when exposed
to water
C - Groundwater inflow through up-
gradient end of landfill
D - Vertical or horizontal percola-
tion from fill to groundwater,
which may contaminate surface
water
E - Leachate seepage
F - Local groundwater flow
Figure 2. Cross section showing water flow into and
away from hypothetical landfill.
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As shown on Figure 2, there are two main sources of water
entering the hypothetical landfill: (1) precipitation falling on
or running onto the landfill and infiltrating into the disturbed
surface, and (2) groundwater flowing from the upgradient side
through the lower portion of the landfill. The leachate produced
initially enters the groundwater and discharges at several side-
hill seeps below the toe of the fill which are highly stained and
odorous. Much of the leachate travels in the groundwater to the
stream and adjacent wetlands where it discharges and has a sig-
nificant detrimental effect. There is a possibility that some of
the leachate may be underflowing the stream (as shown on Figure 2)
and moving into a regional groundwater system, in which case it
could be affecting a number of water supply wells and a stream
that feeds a local reservoir.
In order to stop a landfill from polluting ground and sur-
face waters, it is necessary to (1) control leachate generation
by changing the flow of water through the waste, (2) contain and
remove the leachate produced, or (3) stabilize the waste material
to prevent leaching of deleterious materials. This manual eval-
uates various methods of controlling leachate generation or
retarding its movement. Most of the methods presented are pas-
sive methods of leachate control such as surface and subsurface
infiltration barriers, which require little or no maintenance
compared to active methods such as extraction or injection of
water. All of the procedures included are designed to make the
landfill site a less favorable environment for leachate produc-
tion. These "methods will resuirt—i-n a rc-datction— af—.Leachate
volume; whether or not they decrease the contaminant loading will
depend on the age and condition of the waste.
The manual is organized in five categories: surface water
control, groundwater control, plume management, chemical immo-
bilization, and excavation and reburial. These categories are
presented from least to most technically complicated and costly.
Since potentially there is more than one cause of leachate at a
landfill (e.g., surface water, groundwater, waste pollutant) it
may be necessary to combine methods from several of these cate-
gories to effectively control leachate generation.
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SECTION 2
SURFACE WATER CONTROL
The most accessible part of a waste disposal site is its
upper surface. In many cases, disposal sites are not designed to
minimize the quantity of water infiltrating through the surface.
An extreme example of this is a landfill in a sand and gravel pit
which is not elevated to grade, is covered only with local mate-
rial, and has not been revegetated. The contour and permeability
of the cover in this case insure that nearly all precipitation
falling on the fill is routed to the refuse; and this water
generates large quantities of leachate.
This section presents three methods of reducing infiltra-
tion. The first is changing the contour and runoff character-
istics of the landfill to reroute precipitation. The second is
providing a barrier to infiltration by reducing the permeability
of the land surface. The third is revegetating the site to
stabilize the landfill cover material and increase seasonal
evapotranspiration and interception to control infiltration.
These three methods used together can be very effective in
reducing the amount of water that enters the landfill surface,
and can thereby reduce leachate generation considerably.
CONTOUR GRADING AND SURFACE WATER DIVERSION
Description
Contour grading of a landfill is a means of controlling
and/or diminishing surface infiltration by reshaping the land and
creating hills and valleys to promote and channel surface runoff
(see Figure 3). Grading and compacting the landfill to a profile
of a maximum of 12 percent and a minimum of 6 percent with side
slopes no steeper than 18 percent will allow surface water to
drain from the site and will minimize infiltration. Most soils
will remain stable at these grades. Revegetated landfill sur-
faces that are too flat tend to retain water and increase infil-
tration. Ideally, to minimize overland routing areas subject to
infiltration, the center of the landfill should be the highest
elevation, with slopes of 18 percent maximum toward the landfill
perimeter. Exact slopes to be used must be designed by a compe-
tent professional on the basis of soil type and slope stability
at the site.
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Seeding a Mulching
Diversion Ditch
Contour Grode(6 — 12 percent)
UNCONSOLIDATED EARTH MATERIALS
Stream
BEDROCK
Not to Scale
Figure 3. Cross section of landfill showing contour grading
and surface water diversion.
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Surface water diversion involves creating earth berms and
excavating diversion ditches along the upslope side of the
landfill, directed toward natural drainageways downslope from
the landfill. Diversion ditches are designed to accommodate the
characteristics of the contributing watershed such as area,
annual rainfall, land use, soil type, topography, etc. Most
commonly they are designed for 10-year storm intensity.
Erosion control is an important part of surface water
diversion. Vegetation planted near and on the sides of diversion
ditches will stabilize the soil. However, vegetation takes
between 1 and 2 years to become firmly established. During that
period, mulch and haybales can be used to stabilize these areas.
Mulch can be pegged in place on steeper slopes.
The soils used for the final cover require careful evalua-
tion (see Revegetation section). Such criteria as permeability,
erodibility, fertility, and suitability for the ultimate use of
the completed site must be investigated and documented. County
Soil Conservation Service agencies can be contacted for informa-
tion regarding available cover material and possible sources.
Clayey and silty loams are well suited for final cover.
They are fertile enough to sustain acclimated native vegetation
and are resistant to wind and surface water erosion. Coarse-
grained soils are porous and highly permeable and are therefore
not well suited for final cover. Soils composed predominantly of
clays tend to shrink and crack when dry. Highly organic soils
such as peat are difficult to compact and are usually associated
with a high water content; when dry, they are extremely combusti-
ble and could be a fire hazard.
The distance between cover material borrow areas and the
landfill can be an important cost consideration in final covering
operations. If the distance is great, transportation costs will
be high. The condition of haul roads and bridges must be con-
sidered in terms of the earth loads to be transported.
Decomposing municipal refuse in an anaerobic environment
can generate significant quantities of methane and carbon diox-
ide. These gases can kill vegetation on or near the landfill and
create a potential explosion hazard. Gas generation potential
must be carefully evaluated based on the age, volume, composi-
tion, and moisture content of the waste. If this potential is
high, provisions should .be made for gas venting when the site is
contoured and covered. Methods of gas venting are discussed in
the Surface Sealing section of this manual.
Costs
The cost estimates presented here are based on contour
grading the 4-hectare (10-acre) hypothetical landfill (shown on
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Figure 1) to a maximum of 12 percent and a minimum of 6 percent
slopes with side slopes of not more than 18 percent. This will
involve moving and grading approximately 7,650 m3 (10,000 yd3) of
municipal refuse, using 8,300 m3 (10,750 yd3) of fill material to
complete the grading. The landfill surface will be covered with
a minimum thickness of 0.6 m (2 ft) of soil cover. It is assumed
that the cover and fill material will be transported from a
borrow pit 8 km (5 miles) away. A contingency factor of $2,500
per hectare ($1,000 per acre) is incorporated into the total
costs. Given these conditions, the total cost of grading and
covering the landfill will range between $126,000 and $242,000.
A diversion ditch will be constructed around the upgradient
end of the landfill. It will be 400 m (1,325 ft) long, and extend
halfway down each side of the landfill. Assuming the ditch is
0.6 m (2 ft) deep and 1 m (3 ft) wide, its total cost will range
between $15,000 and $24,000.
Unit cost items 2,-4, and 7, were used in the calculations
(see Appendix). Because contour-graded surfaces must be stabi-
lized with vegetation, the costs of vegetating will also have to
be considered. These costs are presented separately in the
Revegetation section.
Evaluation
Advantages-- . -
1. Construction operation is simple; common construction
equipment is required; and basic engineering principles
are involved.
2. Borrow pits are usually not difficult to find except in
highly developed areas. Earth material can also, be blended
and mixed from several sources.
3. After grading, the landfill can be seeded and mulched to
create large open spaces for recreation.
4. The method can be economical.
5. Covering, regrading, and revegetation of an uncovered,
poorly graded landfill can increase runoff and evapotrans-
piration and virtually eliminate infiltration during the
growing season. Net annual infiltration can be reduced more
than 50 .percent in ideal conditions. (The infiltration
reduction for a particular site can be estimated using the
water balance method.)
Disadvantages—
1. Differential settlement within the contoured landfill will
necessitate periodic regrading to eliminate depressions.
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2. Large quantities of cover material may be required to
establish a slope to induce sheet flow of .surface waters.
3. Suitable borrow pits may be located at a distance from the
landfill, in which case transportation costs would be high.
Recommendations
Grading and surface water diversion measures are effective
and economical standard procedures used in completing landfills.
They promote surface runoff of precipitation, minimize (but not
eliminate) vertical migration of rainfall, cover the landfill,
and protiuce large, gently undulating land areas that can be
revegetated and used for various forms of recreation.
References
For further discussion, see references 1 through 12.
SURFACE SEALING
Description
Surface sealing or capping is a method of landfill closure
that involves the construction of an umbrella cap or seal on the
landfill to prevent water infiltration and minimize leachate
generation (see Figure 4). Caps and seals can be constructed
of clays, fly ash, soils, soil-cement, lime-stabilized soil,
membrane liners, bituminous concrete, and asphalt/tar materials
using common earthmoving construction equipment and procedures.
Stabilized waste materials can also be used for sealing as
described in the Chemical Fixation section.
Prior to construction of any seal, the landfill surface must
be contoured and compacted to provide a firm subgrade. Side
slopes no steeper than 18 percent and top slopes of 12 percent
maximum and 6 percent minimum are recommended. The existing
cover material should be compacted to a Proctor density of 70 to
90 percent of maximum. Less compaction or steeper slopes could
cause seal failure.
If the installation of a native clay seal is to be con-
sidered, field surveys will be required to determine the loca-
tion, availability, and quantity of native clays in the area of
the landfill. Compaction tests and permeability tests are useful
in making these determinations. Where native clays are not
available or available materials are low in clay content, the
seal horizon can be fortified with bentonite clays. Bentonite
can be added at the rate of 2 to 8 kg/m2 (4 to 15 lb/yd2),
depending on the characteristics of the clay, and mixed or disced
into the top 5 to 10 cm (2 to 4 in.) of the seal material.
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4 hectares (lOacres)
Contour Grade (6-12 percent)
Gravel Trench
Mushroom Cop
Gas Vent
Seeding and
Mulching
Max. Slope
percent
46cm-(l8in.) Soil Cover
Cap of Suitable Seal Material
I5m(40-30ft)
Water]
Table
UNCONSOLIDATEO EARTH MATERIALS
Not to Scale
Figure 4. Cross section of capped landfill.
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A bituminous concrete seal can be constructed on the pre-r
pared subgrade of the landfill using either a plant-mixed or job-
site-mixed material. The plant-mixed material can be placed by
asphalt macadam spreader machines and rolled with a 4.5- to 7.3-
tonne (5- to 8-ton) steel-wheel roller. The site-mixed material
can be placed by spreading the aggregate over the entire area,
spraying the bitumen cement over the aggregate, and then placing
a fine aggregate over the bitumen and rolling.
Fly ash is generally available in quantity from fossil-fuel
energy generating systems. Because disposal of this material is
a problem in many parts of the country, it can sometimes be
obtained free of charge within a reasonable hauling distance of
the generating system. However, in some states, fly ash may be
considered a hazardous waste, and special permitting for its use
would be required. Before this material is used for landfill
surface sealing, chemical analyses will be necessary to ensure
that it does not contain unsafe levels of hazardous elements.
In preparing the seal, fly ash can be deposited on the
shaped landfill subgrade and spread by grader and bulldozer.
Wobbly-wheeled (rubber-tired) rollers weighing from 4.5 to 7.3
tonnes (5 to 8 tons) are recommended for compacting the material.
Water can be applied to the surface during compaction to minimize
dust and aid in compaction.
Soil cement and lime-stabilized soils can be used to produce
a sealed landfill surface. These methods involve mixing either
cement or lime with soil and water to provide a relatively im-
permeable seal. A wide variety of soils are adaptable to these
methods; however, sandy and gravelly soils have more favorable
physical characteristics for use with soil cement, and clayey
soils are more adaptable to lime stabilization. Laboratory
analysis of soils is necessary to determine the most appropriate
method as well as the amount of cement or lime required per
unit area of landfill surface. Prior to application of either
material, the entire surface of the landfill must be graded to
the final desired contour. Cement or lime can then be added
to the soil with mechanical spreaders and mixed into the soil.
Commercial mixers/spreaders can also be used to add and mix
the lime or cement as the soil is pulverized, which produces
a uniform distribution of soil and cement or lime over the
entire surface of the landfill. Once the soil and lime or
cement have been completely mixed, water is added by sprinkler
trucks at a rate determined by laboratory testing. The
wetted surface is then rolled for proper compaction and
allowed to cure. The resulting seal is impermeable and has
greater structural integrity than the original soil.
Membrane liner material such as PVC, hypalon, polyethylene,
etc., can also be used as an effective seal for the top surface
of landfills. As with other methods of sealing, a properly
11
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prepared subbase is essential. In this case, the subbase must be
free of foreign materials that might puncture the membrane (e.g.,
sticks, metal, rocks). Abrupt changes in grade should be elimi-
nated and the subbase should roughly conform to the final desired
slope configuration. The membrane is placed over the completed
subbase and the seams between the membrane sections are joined
with heat or adhesive depending on the type of material. Each
manufacturer of membrane liners has a recommended method of
installation and standards for safe and stable cover material.
A soil cover is generally recommended but not always neces-
sary over surface seals. Clay and fly ash are native materials
that do not deteriorate with age. Some asphalt and membrane
materials can be damaged by the sun when exposed, and therefore
must be protected by a soil cover. Other membranes and asphalt
compounds can be left exposed; however, for aesthetic purposes
and/or to prevent vandalism of the seal, a soil cover may be
desirable. At least 46 cm (18 in.) of final earth cover, prefer-
ably a silty or sandy loam, are recommended to support vegetative
growth and protect the seal. The earth cover material can be
transported by truck to the site, spread by grader or bulldozer,
and rolled with a 2.7- to 4.5-tonne (3- to 5-ton) roller.
The sealed and covered landfill must be revegetated to
stabilize the cover material and minimize infiltration (see
Revegetation section). Annual and perennial grasses with roots
not in excess of 38 to 46 cm (15 to 18 in.) are recommended.
Periodic mowing may be necessary to control scrub growth, for
aesthetic purposes as well as to prevent root penetration of the
seal.
If the cover material used is of low permeability, an under-
drain system may be required to ensure lateral drainage above the
seal. An underdrain system can be constructed by laying 30 cm
(12 in.) of 2-cm (0.75-in.) diameter clean stone in a regular
network over the seal. Discharge from the drain is directed away
from the landfill. The drainage field helps to minimize the
amount of water retained in the final cover and direct water away
from the surface seal. It provides further protection against
water infiltrating through the seal into the landfill.
An important consideration in landfill surface sealing is
gas venting. Some kind of opening such as a gravel trench with
mushroom cap vent (shown on Figure 4) or gas venting wells must
be provided to allow escape for the gases formed by decomposing
refuse. The gas can be collected in trenches or wells and, if
sufficient quantities are available, it can be used or sold.
As the landfill ages, the seal and earth cover will be
subject to subsidence and settlement. Maintenance may be re-
quired to fill in depressions to avoid ponding of rain water.
12
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Severe depressions can be corrected by filling in with earth and
revegetating the fill material. If subsidence is severe and
localized, however, the seal will have to be uncovered and
examined for integrity. No other maintenance is anticipated.
Costs
The costs of constructing surface seals given in this sec-
tion include the following:
excavation of 26,700 m3 (34,950 yd3) of common borrow
material [8,200 m3 (10,750 yd3) for contouring to bring
the surface to desired configuration, and 18,500 m3
(24,200 yd3) for the soil cover.]
excavation of 7,700 m3 (10,000 yd3) of the waste during
grading,operations.
earthmoving operations, grading and compacting materials,
equipment and procedures for constructing each seal,
including a contingency factor of $2,500 per hectare
($1,000 per acre).
The costs of the surface seals, complete in place for the
4-hectare (10-acre) landfill, including a 46-cm (18-in.) soil
cover, are estimated as follows:
a. A 15-cm (6-in.) clay cap - $140,100 to $256,200.
b. A 46-cm (18-in.) clay cap - $180,400 to $328,700.
c. A 4-cm (l.Sin.) bituminous concrete cap - $192,500 to
$340,800.
d. A 13-cm (Sin.) bituminous concrete cap - $289,300 to
$437,600.
e. A 30-cm (12-in.) fly-ash cap - $136,100 to $247,300.
f. A 60-cm (24-in.) fly-ash cap - $179,600 to $334,400.
g. A 13-cm (5-in.) soil-cement cap - $209,440 to
$321,440.
h. A 30-cm (5-in.) lime-stabilized cap - $209,440 to
$321,440.
i. A 30-mil PVC membrane cap - $388,800 to $575,500.
The cost of constructing a drainage field above any of these
caps will range between $43,600 and $87,000.
13
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Unit cost items 2, 7, 10, 11, 18, 19, 20, 25, 26, 45, 46,
and 47 were used in these calculations (see Appendix).
The costs of revegetating these surfaces and constructing
diversion ditches, if required, must also be considered (see
sections on Revegetation and Contour Grading).
Evaluation
Advantages—
1. Surface seals can be installed easily and economically.
2. Contractors with equipment for major earthmoving projects
are available throughout the United States.
3. Fly ash may be available free of charge.
4. Soil-cement and lime-stabilized soil construction is
relatively inexpensive and can be accomplished with
locally available equipment.
5. Soil-cement seals do not have to be covered with soil.
6. Lime-stabilized soils can withstand some settlement
without rupture.
7. Bituminous paving can be used to cover large areas rapidly.
8. In landfills where subsidence potential is minor (i.e.,
those with shallow, old we11-compacted wastes), no further
maintenance will be required.
9. Long service life is anticipated.
10. Membrane seals can withstand some settlement.
Disadvantages—
1. The cover and seal are subject to settlement and/or sub-
sidence within the landfill.
2. Vegetation will require maintenance until it has become
firmly established (1 to 2 years).
3. Specific sealing materials:
a. Natural clay deposits may not be available.
b. Fossil-fueled energy stations are not located
in all parts of the country to supply fly ash.
14
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c. Heavy metals in fly ash can be mobilized by
precipitation and cause pollution.
d. Soil-cement caps may rupture with settlement of
the landfill.
e. Membrane materials are expensive.
4. Large quantities of borrow material may be necessary to
establish required slopes on the landfill surface.
5. Gas venting must be provided with all surface seals.
Recommendations
This method when properly maintained can eliminate almost
all infiltration from precipitation into a landfill. Eventually,
this will eliminate further leachate generation from infiltra-
tion. Surface and subsurface discharges of leachate will be
minimized and therefore more easily attenuated by the environ-
ment .
References
For further discussion, see references 13 through 21.
REVEGETATION
Description
Revegetation of a completed landfill helps to physically
stabilize the earth material and reduce infiltration. This
method can be effective as long as there is adequate rainfall to
support plant growth. Although vegetation retards surface run-
off, it serves to minimize erosion of the cover material by wind
and water. By stabilizing the earth materials, vegetation helps
to reduce infiltration of precipitation into the landfill. It
also seasonally reduces infiltration by intercepting and evapo-
transpiring some of the precipitation. A subsidiary benefit is
that vegetation enhances the appearance of the site.
Establishing vegetation on a landfill site first involves
covering the compacted municipal refuse with a suitable, fertile
soil at least 0.6 m (2 ft) thick. The soil preferably should be
a clay loam or silt loam. Sandy loam or soils that are exces-
sively well drained should be avoided as they will allow in-,
creased infiltration of precipitation into the landfill. The
cover material must have sufficient nutrients to support vigorous
plant growth. If these do not occur naturally, soil conditioners
such as organic compost, properly balanced chemical fertilizer,
15
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or digested sewage sludge can be added to attain a satisfactory
nutrient level. If sludge is considered for use as a soil condi-
tioner, it will be important to consult State regulatory agencies
regarding any restrictions or conditions for its use. The
organic materials are preferred because they improve soil struc-
ture and because the nutrients are released more slowly and
remain in the soil far longer than chemical fertilizers.
Prior to planting, the surface must be prepared by grading,
harrowing, discing, or raking. If organic materials are used,
they must be spread over the surface prior to discing so that
they can be worked into the top 5 to 10 cm (2 to 4 in.) of the
soil to provide a supportive seed bed. If a chemical fertilizer
is used it can be applied either with the seed or after plant
growth has been established, depending on the type used.
The chosen mixture of seeds and soil supplements can be
hydroseeded, that is, sprayed onto the landfill surface in a
water mixture. Hydroseeding is the least expensive and the most
cost-effective method of seeding a landfill. Following the
seeding, a mulch consisting of hay, straw, or wood cellulose can
be blown onto the surface to stabilize it while the seeds germi-
nate. On steeper slopes, netting or pegging may be necessary to
hold the seeds, soil, and mulch in place until growth is estab-
lished (1 to 2 years).
In order to determine types of vegetation that would be
suitable for a particular site, soils analyses must be conducted.
Investigations should be made of the soils used for cover, their
pH and fertility, and the slopes of the areas to be covered.
Methods for performing these analyses are generally available
from County Soil Conservation Services.
Vegetation that develops a dense but shallow root system is
more effective both in surface stabilization and seasonal infil-
tration reduction than vegetation with deeper, less dense roots.
Grasses native to the area are the most commonly used type of
vegetation because they establish quickly, especially on fertile
soils, and are easy to maintain. Some that have been success-
fully used on landfill sites include most hay and meadow grasses,
perennial rye, wild-rye, timothy, bentgrass, Bermuda-grass,
Bromegrass, and tall meadow oatgrass. Grassland agriculture
information is generally available through local agencies of the
U.S. Department of Agriculture.
Legumes, such as crown vetch and clover, and crops, such as
alfalfa, are useful in stabilizing areas that slope away from the
landfill (slopes of greater than 20 to 30 percent) and areas
surrounding the fill.
16
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In areas with more than 63 to 76 cm (25 to 30 in.) of
precipitation per year, grass mixtures are recommended on rela-
tively flat lands and grass/legume mixtures on steeper slopes.
Trees and large shrubbery are not recommended for vegetating
landfills because the soil mantle over the refuse is generally
not thick enough to sustain their root systems. If the roots
penetrate the refuse, the vegetation may be killed by gas. A
thicker soil cover than the average 0.6 m (2 ft) [i.e., 0.9 to
1.2 m (3 to 4 ft)] would be required if trees were to be planted
on the completed landfill.
In arid parts of the United States where the climate is not
generally suitable for growing grasses or legumes, native plants
such as creosote bush or salt cedar can be established on the
completed fill. In these areas of the country, water erosion and
infiltration are not as much of a year-round problem but both may
be severe seasonally. Vegetation can be especially useful in
these areas to reduce wind erosion.
A routine maintenance program should be developed for the
first several years after landfill revegetation. Such a program
should provide for repairing cracks in fill areas due to uneven
settlement, reseeding and fertilizing as necessary on the re-
paired areas or on the entire surface if the original ground
cover was an annual variety, and preventing major erosion and
surface water ponding that could provide insect breeding sites
and/or areas of increased infiltration.
Costs
On slopes of less than 12 percent, with a mixture of 20
percent perennial ryegrass, 30 percent red fescue, and 50 percent
Kentucky bluegrass sown at a rate of 11 kg per 1,000 m2 (21 Ib
per 1,000 yd2) with hydroseeding and soil supplements consisting
of pulverized agricultural lime at 432 kg per 1,000 m2 (800 Ib
per 1,000 yd2), urea-form fertilizer (38-0-0) at 27 kg per 1,000
m2 (50 Ib per 1,000 yd2), and commercial fertilizer (10-20-20) at
104 kg per 1,000 m2 (192 Ib pfer 1,000 yd2), costs will be approx-
imately $0.12 to $0.18 per m2 ($0.10 to $0.15 per yd2).
For slopes of 12 percent or steeper, using a mixture of 45
percent preinocculated crown vetch and 55 percent annual ryegrass
sown at a rate of 5 kg per 1,000 m2 (9 Ib per 1,000 yd2) with the
same soil supplements as above, costs will range from $0.12 to
$0.18 per m2 ($0.10 to $0.15 per yd2). As an alternative, crown
vetch crowns can be used. Crown vetch crowns [started plants in
8-cm (3-in.) pots] cost from $0.25 to $0.35 each and are planted
at a rate of 1.2 per m2 (1 per yd2) on steep slopes where a rapid
cover is required.
17
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Mulching with straw or hay at a rate of 540 kg per 1,000 m2
(1,000 Ib per 1,000 yd2) costs between $0.06 and $0.12 per m2
($0.05 and $0.10 per yd2). Mulching with wood cellulose, which
is often used on steeper slopes, costs between $0.12 and $0.24
per m2 ($0.10 and $0.20 per yd2).
Costs of seeding and mulching the hypothetical 4-hectare
(10-acre) landfill with slopes of less than 12 percent will range
from $7,300 to $12,000. Seeding and mulching of a 4-hectare (10-
acre) landfill with steeper slopes will cost between $12,000 and
$26,600.
The unit cost items used in these calculations are items
29 and 30 (see Appendix).
Evaluation
Advantages—
1. Vegetation stabilizes the final cover material and helps
minimize erosion.
2. It seasonally reduces infiltration into the landfill.
3. It enhances the appearance of the site.
4. The method is inexpensive and cost-effective.
5. Procedures are uncomplicated and equipment is minimal.
Disadvantages—
1. Vegetation requires 1 to 2 years to develop an established
root system. Inadequate cover soil fertility or settlement
of the landfill can interfere with the establishment of
vegetation.
2. Initial erosion control may be difficult until a sufficient
amount of vegetation is in a stage of vigorous growth to
stabilize the soil.
3. In stepped landfills, leachate breakouts can kill vegeta-
tion.
4. Gas venting provisions must be made to prevent gas migration
which could kill vegetation.
Recommendations
Ground preparation and seeding are essential parts of
closing or upgrading a landfill. In flat areas, seeding should
be completed between March 1 and June 1 or between August 1 and
October 1. Sloped areas can be seeded (with legumes) at any time
of year except during September and October.
18
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The use of trees or shrubs on newly covered landfills is not
recommended; their deep root systems can penetrate the refuse and
either break the cover, kill the plant, or both.' The plants that
can be established in arid areas nearly always have deep root
systems. Therefore in arid areas unless the cover materials on
the landfill are deep the site should be left to volunteer vege-
tation.
Vegetation is an inexpensive and cost-effective method of
stabilizing the surface of a landfill and of reducing leachate
generation to some degree during the local growing season. When
used as part of a properly managed leachate control program,
revegetation has been shown to be an effective landfill comple-
tion method.
References
For further discussion, see references 7 through 12 and 22
through 34.
19
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SECTION 3
GROUNDWATER. CONTROL
Where the landfill extends below the water table, ground-
water flows through the landfill and produces considerable
quantities of leachate. Most of the areas in .which this occurs
are underlain by unconsolidated materials and have groundwater at
relatively shallow depths. In such cases, a physical barrier can
be constructed to prevent movement of groundwater through the
refuse. A properly constructed groundwater barrier will lower
the water table in and around the landfill so that the refuse
is no longer saturated and leachate generation is reduced.
This section presents methods of constructing a barrier on
the upgradient side or the bottom of a landfill to control
groundwater movement. These methods have considerable potential
for reducing leachate generation in areas where the landfill
extends below the water table and for isolating the disposed
wastes when used in conjunction with top sealing methods.
BENTONITE SLURRY-TRENCH CUTOFF WALL
Description
A slurry-trench cutoff wall is an underground water barrier
used to prevent horizontal subsurface movement of leachate away
from a landfill. Essentially, the construction process entails
digging a trench, filling it with bentonite slurry as excavation
progresses, and backfilling the slurry-filled trench with the
excavated material. The bentonite slurry supports the trench.
sides during excavation. Figures 5 and 6 show slurry-trench
cutoff wall construction at the hypothetical landfill. The wall
acts as a barrier to divert groundwater flow beneath and away
from the landfill. A properly designed cutoff wall lowers the
water table so that it no longer flows through the landfill.
Encircling the landfill, while effective, may not be necessary.
The slurry-trench cutoff wall can lower the water table in
the landfill by (1) providing a complete seal by extending the
cutoff wall to an impermeable layer, or (2) by increasing the
length of the groundwater flow path and hence the energy loss as
shown in Figure 6. In the latter case, the cutoff wall forces
the groundwater to flow a longer distance beneath the wall and
20
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SLURRY-TRENCH CUTOFF WALL
GROUNDWATER
FLOW
Figure 5. Plan view of semicircular slurry-trench
cutoff wall around upgradient end of landfill.
21
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Leocnote
\ Seepoge
_—Stream
UNCONSOLIOAT E 0
EARTH MATERIALS
(a)
UNCONSOLI DATED
EARTH MATERIALS
(b)
Figure 6. Cross section of landfill
before (a) and after (b) slurry-trench
cutoff wall installation.
22
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also diverts it laterally around the site. As water flows under
the wall, it loses energy and therefore does not rise as high on
the downgradient side as it would without the cutoff wall. The
energy loss is represented by the gradient (slope) of the water
table. The cutoff essentially lengthens the aquifer through
which the water flows (see Figure 6). The lowering of the water
table on the downslope side of the cutoff wall is equal to the
increase in the effective length of the aquifer times the gradi-
ent (energy loss) over that distance. There.will also be some
reduction in water table elevation due to diversion of water
around the landfill because the aquifer will have a smaller cross
section and therefore less carrying capacity (see Figure 6).
The length and depth of the trench required must be determined by
the depth to groundwater and the type of earth materials under-
lying the particular landfill. A slurry-trench cutoff wall can
be constructed with equipment in general use throughout the
construction trade. Deep trenches can be excavated with a clam-
shell bucket or dragline bucket, and shallow trenches with back-
hoe/pull-shovel equipment. Trenches to depths of 25 m (80 ft)
have been successfully completed.
Sodium bentonites, which are natural clay substances mined
in Wyoming, South Dakota, and Montana, are typical materials used
for constructing slurry-trench cutoff walls. When mixed in
water, sodium bentonite becomes sheathed in a protective film of
water molecules which causes the clay particles to swell. When
the water is absorbed, the effective diameter of the particles is
increased and, at the same time, a portion of the water in which
the clay is suspended is inactivated. There is a resultant
increase in the density of the mixture, making the specific
gravity greater than that of water.
When placed in the trench, the slurry enters any exposed
voids in the walls. The hydrostatic pressure created by the
slurry forces the water from the voids, and the bentonite parti-
cles begin layering within and around them, forming a cake or
diaphragm that completely chokes the openings. As the diaphragm
builds up, it becomes impervious to penetration by groundwater,
and water loss from the slurry through the trench wall decreases.
The diaphragm prevents sloughing of the trench walls, and the
outward pressure of the slurry prevents cave-ins.
The bentonite slurry introduced into the trench generally
should weigh between 1,041 and 1,121 kg/m3 (65 and 70 Ib/ft3).
This density will increase during excavation because fine par-
ticles tend to become suspended in the slurry. The slurry must
be premixed in a batch plant using a ratio of approximately
1 part bentonite to 12 parts water. The density of the slurry
can be maintained at the desired levels by recirculating it
through a recovery system when it becomes too heavy, and by
adding more bentonite to the slurry when it becomes too light.
23
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After excavation has begun, and as soon as it reaches the
groundwater table, the slurry should be introduced into the
trench. The level of the slurry should be maintained above the
groundwater table as the excavation proceeds to the desired
depth.
During trench excavation, the excavated material which has
been soaked by the slurry is cast near the trench to allow excess
.slurry to drain back into the trench. The backfill material is
then deposited back into the trench 60 to 150 m (200 to 500 ft)
behind the excavation operation. Backfilling can be accomplished
with a bulldozer or front-end loader. As the backfill material
drops through the slurry in the trench, the bentonite layering or
caking action takes place throughout the thickness of the slurry-
trench mass to establish an effective cutoff wall impervious to
groundwater. The displaced slurry is then reclaimed and pro-
cessed for reuse. The backfilled trench does not need compac-
tion.
Costs
A slurry trench 18 m (60 ft) deep and 1 "m (3 ft) wide will
range in cost between $294 and $495 per lineal foot complete in
place. To construct a semicircular cutoff wall 518 m (1,700 ft)
long around the upgradient end of the 4-hectare (10-acre) land-
fill will cost between $499,800 and $841,500, complete i'n place.
Unit cost items used in these calculations are items 2, 6, and 13
(see Appendix).
Evaluation
Advantages--
1. Construction methods are simple.
2. Adjacent areas will not be affected by groundwater drawdown.
3. Bentonite is a mineral and will not deteriorate with age.
4. Leachate-resistant bentonites are available.
5. Once the cutoff wall is constructed, no further action or
maintenance will be required.
Disadvantages—
1. The cost of shipping bentonite from the west to the site
must be considered.
2. Several aspects of the construction procedures are patented
and will require a license.
3. In rocky ground, over-excavation will be necessary because
of boulders.
24
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4. Common bertonite deteriorates when exposed to high ionic
strength leachates.
Recommendations
This method can be effective in rerouting the flow of ground-
water, preventing subsurface infiltration, and containing leach-
ate generated in the landfill. Ideal conditions for effective
use of a slurry-trench cutoff wall include a relatively shallow
water table, an aquifer of moderate permeability, and a rela-
tively shallow depth to bedrock or other aquifer. Contour
grading and revegetation of the landfill surface to promote
runoff of precipitation and minimize surface infiltration is
recommended (see Contour Grading and Revegetation sections).
References
For further discussion, see references 35 through 46.
GROUT CURTAIN
Description
A grout curtain is created by injecting solutions or water/
solid suspensions under pressure into soils and underlying earth
materials as a groundwater barrier. The grout solution fills the
voids in the soil and thereby minimizes or stops the flow of
water.
In landfill neutralization, the grout is injected vertically
to predetermined depths around the upgradient end of the landfill
to create a curtain or wall of grout which diverts groundwater
flow as shown on Figure 7.
The type of grout must be selected on the basis of the soils
and geologic conditions present at the landfill. Geotechnical
investigations are a critical phase of grout curtain projects.
Accurate test borings, core sampling, and laboratory analyses for
porosity, hydraulic conductivity, and connected pore volume must
be conducted to determine the best grouting materials and methods
to be used under the existing site conditions.
The most common types of grout are cement, bentonite, and
chemical. Several more specialized grouts are epoxy resins,
silicone rubbers, lime, fly ash, and bituminous compounds. Each
grout can be used to fill a certain sized void in the earth
materials present. The permeability of the soil will determine
the type of grout that can be injected into the soil pores.
Figure 8 indicates the types of grout that will be effective in
various soils, based on their effective grain size. Combinations
of these grouts may be used to seal different types of soils
encountered at the site.
25
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UNCON SOLI DATED
EARTH MATERIALS
Figure 7. Cross
section of grout curtain at landfill,
-------
GRAVEL
FINE
SAN 0
COARSE
MEDIUM
FINE
CLAY -SOIL
COARSE SILT
SIUT(NONPLASTIC)
INI
mi
III!
1 1 1 II 1
INI
Mil
._.
II
Re
II
Chrome-Lignin
1
sins
| Silicates
INI
mr
mi
>«
T1
e
la
e'nt
nd c
onite
6 merit
A
Ch<
t(
w
A-
ni(
9
:al
gra
ut
100
I-O 0.1
GRAIN SIZE (MM)
0.01
0.001
Figure 8. Soil limits of grout injectability
(from American Cyanamid Co.,
reference 48).
27
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Prior to use, the selected grout mixture should be tested by
injection into a prepared soil sample from the site. The flow
rates of the grout through the soils should be measured under
different pressures. Soil permeabilities should also be measured
before and after the grouting to determine its effectiveness.
(Test procedures are detailed in reference 47.)
Once the grout has been selected and tested, the curtain can
be designed. The curtain is formed by arranging two or three
rows of pipes offset from each other in a grid pattern over the
area to be seciled (see Figure 9) , and injecting grout through the
pipe at successive depths. The resulting curtain is shown in
Figure 10. Grout pipe is commonly extended to a maximum of 15 to
18 m (50 to 60 ft). Deeper injections may require heavy-duty
driving equipment.
The spacing in the grid pattern can be determined by formula
so that when injected, the grout will spread outward at least
half the distance between the pipes before setting to fill the
pore spaces throughout the grouted area. Thus, a continuous wall
will be formed. The preliminary grout and soil tests will be
helpful in determining pipe spacing.
The rate of grout injection will be a function of the type
of grout and the subsurface conditions at the site. Cement grout
sets up in approximately 4 hours, whereas some chemical grouts
set up within seconds after placement. A volume of 11 to 19
liters/min (3 to 5 gal/min) can be assumed as an average rate for
grout injection.
Costs
When several grouts are suitable for a particular applica-
tion, the cost of grout may determine the order of preference.
Table 1 indicates the relative cost basis of various chemical
grouts compared with cement. Injected complete in place, port-
land cement grout costs between $142 and $357 per m^ ($4.00 and
$10.00 per ft3).
To install a 518-m (1700-lineal ft) cement, grout curtain
cutoff wall in a horseshoe configuration on the upgradient side
of the 4-hectare (10-acre) landfill to a depth of 18 m (60 ft)
will cost between $801,300 and $2,003,000, using a two-row grid
pattern with pipes on 1.5-m (5-ft) centers, and injecting a
Portland cement grout with a 5 to 1 water-cement ratio in coarse
sand with a porosity of 25 percent. Unit cost item 14 was used
in these calculations (see Appendix).
28
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to
B
: •'!
v--x^
\
o
/ \
1.5m
(5 ft)
°
\
Figure 9. Typical two-row grid pattern for grout curtain
-------
Semi circular.
Grout Curtain /
CO
o
Grout Tubes
518m
11700 ft)
Figure 10. Semicurcular grout curtain around
upgradient end of landfill.
-------
TABLE 1. RELATIVE COSTS OF GROUT*
Type of Grout Basic Cost Figure
Portland cement 1.0
Silicate base - 15 percent 1.3
Lignin base 1.65
Silicate base - 30 percent 2.2
Silicate base - 40 percent ' 2.9
Urea formaldehyde resin 6.0
Acrylamide (AM-9) 7.0
*Base unit = 1.0. Under a given set of conditions, where port-
land cement grout costs 1.0 times $/unit, other types of grout
will cost the given figure times $/unit.
31
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Evaluation
Advantages—
1. When designed on the basis of thorough preliminary investi-
gations, curtain grouting can be very successful.
2. . The method is well established; it has been in use for over
100 years in construction and stabilization projects.
3. There are many kinds of grout to suit a wide range of soil
types.
Disadvantages—
1. Grouting is only effective in soils with permeabilities of
10~5 cm/sec or greater.
2. Some grouting techniques are proprietary.
3. Because grouting involves subsurface construction, the
procedure requires careful planning and pretesting. Methods
of ensuring that all voids in the wall have been effectively
grouted are not readily available.
4. Chemical grouts are expensive.
Recommendations
An in-depth field and laboratory investigation is essential
in the design of an injection curtain cutoff wall.
Grouting is considered a feasible solution in consolidated
sand or cohesionless soils. Chemical grouts must be used in fine
sands and silts to a permeability of 10"^ cm/sec. Grouting alone
cannot be considered a cure-all. It is recommended that this
method be combined with other corrective measures such as grading,
seeding, and mulching to minimize surface infiltration.
References
For further discussion, see references 38, 41, and 47
through 51.
SHEET PILING CUTOFF WALL
Description
Construction of a sheet piling cutoff wall involves driving
lengths of steel sheet piling permanently into the ground with a
pile-driving hammer. Lengths of sheet piling over 30 m (100 ft)
have been successfully placed.
32
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Sheet piling is a web section of steel with an interlocking
device along both edges, consisting of either a socket end or
bowl-and-ball end. Various shapes and weights of steel sheet
piling are available in standard lengths for use in different
types of earth materials. The most common shapes are the Z-type,
pan or hat type, and straight types. Weights of sheeting range
from 107 kg/m2 (22 Ib/ft2) for the pan type to 185 kg/m2 (38
Ib/ft2) for the Z-type.
The sections are assembled before being driven into the
ground. When first installed, the sheet piling wall is not
watertight due to mill tolerances in the interlocking edges.
With time, these edges self-seal with the fine sediment carried
by seeping water.
The sheet piling wall shown in Figure 11 is designed to
retard the flow of water under and through the landfill. If the
soils were extremely permeable, the groundwater would rise too
quickly under the landfill and it would be necessary to extend
the piling to bedrock to dewater the landfill.
The service life of steel sheet piling at installations
around the country has far exceeded the theoretical estimate of
performance, especially in soils where .adverse conditions and
chemicals have been present. Corrosion of the metal does not
appear to be a factor in_causing failures in the .structure.
Inspections of pilings in place ranging in age from 7 to 40
years, in soil types ranging from well-drained sands to imper-
vious clays, with soil resistivities ranging from 300 ohm-cm to
over 50,000 ohm-cm, and soil pH ranging from 2.3 to 8.6 indicated
that the type and amount of corrosion was not sufficiently sig-
nificant to affect the material's strength or useful life.
Cathodic protection is suggested for submerged piling.
Properly spaced sacrificial anodes will provide adequate pro-
tection.
Costs
A steel sheet piling cutoff wall installed at the upgradient
end of the hypothetical landfill will have soil material on both
faces; therefore, a light section will be adequate in this case.
The lightest section made is designated PMA 22 (AISI standardized
section designation) and weighs 107 kg/m2 (22 Ib/ft2).
Costs were developed assuming a sheet piling cutoff wall
518 m (1,700 lineal ft) long and 18 m (60 ft) deep. The sheet
piling distributor closest to the east coast hypothetical land-
fill is located near Buffalo, New York. Material costs (F.O.B.
plant) are $37.00 per 100 kg ($16.80 per 100 Ib). Truckload
permits are $24.75 and shipping charges are $3.65 per 100 kg
33
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OJ
Water Table-?
"~ ' -- —i — *_
UNCONSOLI DATED
ARTH MATERIALS
Figure 11. Cross section of sheet piling cutoff wall
at landfill.
-------
($1.65 per 100 Ib) [$7.25 per 20-tonne load ($660 per 20-ton
load) from Buffalo, New York to the Philadelphia area] for total
shipping charges of $38,450.
Total costs to construct and install the sheet piling cutoff
wall then will be $650,500 to $956,500, complete in place. Unit
cost item 22 was used in these calculations (see Appendix).
Evaluation
Advantages—
1. Construction is not difficult; no excavation is necessary.
2. Contractors, equipment, and materials are available through-
out the United States.
3. Construction is relatively economical.
4. Once the cutoff wall is installed, no further maintenance or
action will be required.
5. Steel can be coated for protection from corrosion to extend
its service life.
Disadvantages—
1. The steel sheet piling initially is not watertight because
of manufacturing tolerances.
2. Driving the piling through ground containing boulders is
difficult.
3. Exotic chemicals, if present, may attack the steel.
Recommendations
A steel sheet piling cutoff wall is a maintenance-free means
of preventing groundwater flow through a landfill. To minimize
surface infiltration, it is recommended that the landfill also be
contour graded and revegetated.
References
For further discussion, see references 52 through 57.
BOTTOM SEALING
Description
This neutralization alternative involves creating a bowl-
shaped bottom seal beneath the site and isolating the landfill
from the groundwater (see Figure 12). The seal is constructed
by pumping or pressure-injecting grout under the existing land-
35
-------
U)
(Tv
_ Min. |.5m (5f») soil layer
UNCONSOLI DATED EARTH MATERIALS
Figure 12. Cross section of grouted bottom seal
beneath landfill.
-------
fill through tubes placed through the fill at regular intervals.
Portland cement grout, leachate-resistant bentonite slurry, or
chemical grout can be used. Some methods of pressure grouting
have been patented.
Initially, exploratory boreholes must be drilled to deter-
mine the limits of the landfill both vertically and horizontally.
The. entire site must be gridded with permanent survey references.
The grid pattern can be based approximately on 1.5- to 1.8-m
(5- to 6-ft) centers. Exploratory boreholes should be drilled on
30-m (100-ft) centers to determine the lowest elevations of the
refuse; and a contour map of the landfill bottom should be pre-
pared. The boreholes should be extended at least 6 m (20 ft)
below the refuse to sample the underlying material.
The material being grouted, e.g., clay, sand, silt, gravel,
must be tested and identified so that the appropriate type,
amount, and application rate of the grout can be determined.
In the seal installation, the grout tubes are extended from the
surface in a grid pattern to below the landfill. A layer of
soil a minimum of 1.5 m (5 ft) thick or the thickness of the
grout liner should be left between the grouted material and the
refuse to allow for irregularities in the bottom of the landfill.
The liner can be between 1.2 and 1.8 m (4 and 6 ft) thick. The
grout is pumped under pressure through the tubes and driven into
the voids in the soil. It then hardens into a permanent liner.
The bowl-shaped seal will be effective in containing leach-
ate in the landfill. If extended high enough, it can prevent
groundwater from flowing into the fill where the water table is
above the bottom of the landfill. The leachate contained in the
fill can then either be pumped out and treated, or remain iso-
lated in the landfill.
Further leachate generation must be controlled, however, so
as not to exceed the capacity of the bowl. The landfill surface
should be contour graded and revegetated to promote surface
runoff and minimize vertical infiltration of precipitation.
Costs
The costs of constructing a grout bottom seal will vary
depending on the permeability of the grouted materials. To
construct a 1.2-m (4-ft) thick portland cement bottom liner
under the entire 4-hectare (10-acre) landfill will range in cost
as follows depending upon the soil permeabilities: with 20
percent voids, $1,115,000 to $2,786,000; with 30 percent voids,
$1,672,000 to $4,180,000.
A 1.8-m (6-ft) thick liner under the landfill will range in
cost as follows: with 20 percent voids, $1,667,000 to $4,166,000;
with 30 percent voids, $2,500,000 to $6,250,000.
37
-------
The cost of the exploratory boring program based on the
recommendations presented in this section will range between
$7,600 and $25,000.
These estimates are based on unit cost items 14 and 24 (see
Appendix).
Evaluation
Advantages—
1. Grouting has been a standard practice for many years and is
very effective in gravel and sand.
2. Construction is relatively easy and can be performed at any
time of year.
Disadvantages—
1. Drilling through the refuse may be difficult because of
unknown materials.
2. The grout-take may be erratic when uncharted pockets of
fine-grained soils, are encountered.
3. Methods of determining that all voids between boreholes have
been effectively grouted are not readily available. After
installation, an ungrouted void would be difficult to locate.
4. Overdesign of the grout barrier is almost unavoidable
because of the uncertainties involved in creating a solidi-
fied mass beneath the landfill to prevent seepage.
5. Bottom sealing has not yet been used on landfills and leach-
ate may have a deleterious effect on the grout integrity.
Recommendations
Bottom sealing with grout is especially effective in coarse-
grained soils and gravels up to depths of 90 m (300 ft). The
isolation barrier formed by the grouted soil can effectively
control leachate movement into the groundwater. Contour grading
and revegetation of the landfill surface are recommended in
support of the liner installation.
References
For further discussion, see references 38, 41, and 47
through 51.
38
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SECTION 4
PLUME MANAGEMENT
Methods of plume management are designed to improve ground
and surface water quality around a landfill by actively altering
the course of leachate movement. They generally involve either
the addition or removal of water by pumping or drainage from
around the landfill. These methods require a continuing input of
energy to the hydrologic system, usually in the form of power for
pumping water. They also require continued maintenance. How-
ever, because they actively add or remove groundwater they can
effect greater changes in water table elevations than can passive
barriers.
The first category of plume management methods involves
groundwater extraction. All groundwater extraction methods are
designed to lower the water table by collecting groundwater
and/or leachate. These methods are similar in purpose to sub-
surface infiltration barriers, passive methods of leachate con-
trol.
The second plume management category is injection, that is,
the addition of water to the groundwater either to flush contami-
nants from the refuse or to redirect the movement of leachate.
Injection is most often used to recycle the leachate removed from
extraction wells back onto the refuse cell. Its other applica-
tions, such as injection/extraction barriers, would be useful in
protecting an important water supply from leachate encroachment.
Plume management measures often involve leachate collection
and handling (i.e., treatment, recycling, or disposal). Several
methods of leachate management are discussed and evaluated in
this section.
EXTRACTION
Description
There are three basic means of removing water and/or leach-
ate from the ground: drains, well point systems, and deep well
systems. Each of these systems can be used either upgradient or
downgradient of a landfill. In an upgradient situation, the
purpose of the system is to intercept water which would otherwise
39
-------
have saturated the lower portion of the landfill and caused
leachate generation. To ensure that the fill is actually de-
watered by the cone of depression developed, these systems must
be placed close to the upgradient end of the fill. This means
that even though the upgradient system is designed to intercept
mainly uncontaminated water, it might also intercept and collect
some leachate. Therefore the water may not always be directly
discharged to surface water. Recirculation or treatment systems
may be necessary to handle contaminated groundwater.
Extraction systems located downgradient of the landfill are
placed so as to intercept the leachate and groundwater as it
flows from the landfill. Commonly the system is relatively
shallow, unless leachate is moving downward beneath the landfill
in which case the system must be relatively deep.
Drains—
The purpose of drains is to intercept groundwater and carry
it away. They can be used to lower the water table a few feet or
to channel and collect leachate to prevent sidehill seeps and
seepage into surface water bodies (see Figure 13). Drains are
widely used to reclaim swamp land for agriculture, and construc-
tion techniques for their emplacement are well developed.
Drains are constructed by excavating a trench, partially
backfilling it with sand or gravel, placing either a plastic or
ceramic drain tile in the sand and gravel bed, and completing the
backfilling. To prevent clogging of drains by the surrounding
soils, the backfill material must be only slightly more permeable
than the surrounding material.
Well Point Systems—
Well point systems can be used to lower the water table
several feet and/or to collect leachate. They are commonly used
to lower the water table at construction sites. Well point
systems have a limited radius of influence, governed by the
hydraulic conductivity of the material in which they are emplaced.
Suction is used for extraction in these systems, which limits the
depth of extraction to 10 m (30 ft). They can provide drawdowns
of up to 4.5 m (15 ft) in their immediate vicinity. In order to
determine the spacing required for the wells and the effective-
ness with which they can be used, a hydrogeologic study of the
aquifer characteristics of the area, including a pump test, must
be conducted prior to design of the system.
In the installation of well point systems, short lengths of
well screen on 5- to 7.5-cm (2- to 3-in.) pipe are installed by
jetting on 1- to 1.5-m (3- to 5-ft) centers in a line up- or
downgradient from the fill (see Figure 14). The well points are
connected to a suction header and the header is connected to a
pump which evacuates the air from the well points and the header.
This vacuum results in external pressure which forces the ground-
40
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UNCONSOLIDATEO
EARTH MATERIALS
BEDROCK
Not to Scale
Figure 13. Cross section of drain downgradient
from the landfill.
-------
WELL
POINTS
OR
.EXTRACTION
WELLS
STONE -
FILLED
TRENCH
FOR RECHARGE*
•''•Assumes no leochote
collected with groundwoter
Discharge From
Wells to Trench
DISCHARGE
PIPE
Figure 14. Plan view of well points or extraction
wells used to lower the water table upgradient
from the landfill.
42
-------
water to flow through the well points. Since this is a vacuum-
operated system, it is necessary that all portions of the well
point header system be completely airtight. For permanent
installation, such as at a landfill, the header would be buried
in a trench, preferably below frost line. PVC is the recommended
construction material for the well points and a header handling
leachate. The collected water can be discharged either to a
stone-filled trench for recharge to the groundwater or discharged
to the surface water. If contaminants are present, leachate must
be treated before discharge.
If dewatering depths of greater than 3 to 5 m (10 to 15 ft)
are needed, more than one stage of well points would be neces-
sary. The second stage of well points would be installed 2 to
2.5 m (6 to 8 ft) below the first stage.
Deep Well Systems—
Deep well systems are useful for dewatering soils in cases
where a large vertical interval must be dewatered (see Figure
15). In a deep well system, each well is equipped with its own
pump, and the lift is not limited to suction as in a well point
system. Thus deep well systems can dewater at much greater
depths than well point systems. Deep wells are capable of low-
ering the water table as much as 12 m (40 ft) in uniform sand.
However, the initial investment in a deep well system is gener-
ally higher than in a well point system, since it requires more
materials and equipment and is significantly more expensive to
install.
A hydrogeologic evaluation of the aquifer, including aquifer
testing, must be conducted before a deep well system can be
designed. Depending on the permeability of the geologic mate-
rials, the spacing between the wells may vary from a few feet
to perhaps 30 m (100 ft) with a well depth of 9 to 18 m (30 to
60 ft).
Costs
Drains—
Shallow drainage by trenches or subgrade drains costs on the
order of $1,235 to $1,730 capital cost per hectare drained ($500
to $700 per acre of landfill drained), depending on the depth of
placement and materials used. Labor and maintenance costs are
$1,545 per year. The cost of operating the system for 20 years
in current dollars is $16,900; the total cost to drain a 4-
hectare (10-acre) landfill is $21,900 to $23,900.
Dewatering by Well Points or Deep Wells—
Well point systems cost $30 to $33 per m ($9 to $10 per
lineal drain ft) for installation of well points and headers,
plus $2,000 to $3,000 for a 19- to 25-liter/sec (300- to 400-
43
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Stone-filled trench
Water table
before
pumping
UNCONSOLIDATED
EARTH MATERIALS
Water table with pumping
Stream
BEDROCK
*A«tumes no leochgte collected with groundwoter
Not to Scale
Figure 15. Cross section of extraction well at landfill
-------
gal/min) pump. To drain a 275-m (900-lineal-ft) area upgradient
of a landfill therefore would cost approximately $12,000 (capital
cost).
Deep well dewatering systems cost approximately $50 per m
($15 per ft) for a 10-cm (4-in.) PVC well plus $100 for a screen
and $800 to $1,000 for a pump. Using nine 18-m (60-ft) deep
wells to drain a 275-m (900-ft) front would cost $18,000 for
installation of the wells and pumps plus the cost of connecting
electric service.
A number of additional costs common to both well point and
deep well dewatering systems are the costs of electric power,
pretesting, pretest analyses, and system design and engineering.
Electric power costs for either system would be approxi-
mately $10,500 per year, based on a 32-kw (24 hp) demand at $0.07
per kWh.
Pretesting is essential to ensure proper design of any
dewatering system. A test well 18 m (60 ft) deep constructed as
above would cost approximately $1,000. Three piezometers at a
cost of $16 per m ($5 per ft) at a depth of 18 m (60 ft) would
also be necessary, at a cost of $900. A 12-hour airlift pump
test at $30 per hour would cost $360 for a total approximate
pump test cost of $2,000.
Analysis of the pump test by a competent hydrogeologist
would cost $2,500 to $4,000, depending on the complexity of the
aquifers.
System design and engineering costs would run between $5,000
and $10,000 depending on the complexity of the electrical and
mechanical work and the hydrogeologic situation.
In summary, the costs for dewatering a 275-m (900-lineal-ft)
area upgradient of the landfill are estimated as follows:
Well point system $12,000
Pump test 2,000
Pump test analyses 2,500 - 4,000
System design and
engineering 5,000 - 10,000
$21,500 - $28,000 capital
Labor/year $ 3,100
Material/year 1,080
Power/year 10,500
$14,680 x 10.91* = $160,200
Total Present Worth: $181,700 - $188,200
45
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Deep well system $18,000
Pump test 2,000
Pump test analyses 2,500 - 4,000
System design and
engineering 5,000 - 10,000
$27,500 - $34,000 capital
Labor/year $ 3,100
Material/year 386
Power/year 10,500
$13,986 x 10.91* = $152,600
Total Present Worth: $180,100 - $186,600
*The present worth calculation factor is based on
6-5/8 percent interest for 20-year power, opera-
tion, and maintenance costs.
These calculations are based on unit cost items 31 through 37 and
39, 43, and 44 (see Appendix).
Evaluation
Advantages—
1. Construction methods are relatively simple.
2. Actual removal of water and/or leachate from the landfill is
effected.
3. Groundwater resources are protected by positive action.
4. Installation is not overly expensive.
Disadvantages—
1. Power costs are high.
2. Continued maintenance is necessary to prevent system mal-
function.
3. With well point systems, fairly constant supervision is
required to insure that suction is maintained in the system.
4. Pumping requires a long-term commitment of both manpower and
material.
5. Extracted water may be contaminated with leachate and have
to be treated before it is discharged.
46
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Recommendations
Extraction methods can be extremely effective in reducing
leachate generation by groundwater or preventing leachate flow
to undesired areas. They are, however, expensive and require a
long-term commitment to the maintenance of the landfill. Re-
grading and revegetation of the landfill are recommended to
reduce the quantity of leachate generated by infiltration.
References
For further discussion, see references 58 through 67.
INJECTION
Description
The second plume management technique involves the intro-
duction of water or leachate into the groundwater either through
or around the landfill. Water or leachate may be introduced
through well points or deep wells, or it may be spread on the
surface in seepage beds or trenches.
The purpose of introducing clear or uncontaminated water
into the aquifer is to provide a barrier to leachate movement.
This technique has been used mainly to prevent intrusion of salt
water into aquifers. If, for instance, the leachate plume was
moving 'toward a municipal well field, it might be effective to
create a groundwater mound between the leachate plume and the
well field to redirect its course. A critical concern in cre-
ating an injection barrier is finding an alternate direction of
travel for the leachate plume. The leachate must either be
attenuated on its new course and mixed with groundwater to harm-
less concentrations, or discharged at some point where it causes
no harm to the receiving water body. Deep well injection would
generally only be used if a shallow, potable aquifer was under-
lain by a deep, highly mineralized and unusable aquifer, with
good hydraulic isolation between them. In such a case, if not
restricted by local law, leachate could be extracted from the
shallow (potable) aquifer and injected into the deeper (non-
potable) aquifer. A detailed hydrogeologic investigation is
required to ensure that the leachate is contained and does not
migrate or cause other contamination problems. Shallow well
injection can be used to introduce leachate into the landfill
itself and, as such, is discussed under the Leachate Handling
section herein.
Costs
An injection/extraction barrier would cost roughly twice as
much as a deep well extraction system because twice as many wells
would be required in addition to transmission and control equip-
47
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ment. Thus costs for installation of an injection/extraction
barrier at the 4-hectare (10-acre) site are estimated at $35,000
to $36,000. The labor, material, and power costs would be
approximately $15,000 per year plus electrical service connection
fee for a present worth of $163,700 for 20 years. The total cost
would be $198,700 to $199,700. (See unit cost items 34, 35, 36,
40, and 43 in Appendix.)
Evaluation
Advantages—
1. Injection into a landfill can accelerate refuse stabiliza-
tion.
2. An injection barrier provides a positive means of halting
the speed of leachate at any depth.
3. Deep well techniques for the design and emplacement of
injection/extraction barriers are well documented.
4. Injection of leachate results in its permanent disposal.
Disadvantages—
1. Establishment of an injection/extraction barrier initially
requires large amounts of water. The water may not be
reusable after is is re-extracted.
2. With barriers, the plume is redirected rather than removed.
3. Initial and maintenance costs are high, especially for
corrosive or hard water.
4. Careful management is required to avoid contamination of
other aquifer areas.
Recommendations
Injection barriers can best be used to protect a valuable
water resource when a large area is involved or when installation
of a physical barrier is not possible, as in a bedrock aquifer.
Regrading and revegetation are recommended to reduce infiltration
and the quantity of leachate generated.
References
For further discussion, see references 64, 66, and 68.
LEACHATE HANDLING
Description
Once leachate has been intercepted and collected, it can
48
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either be recycled through the landfill to be treated and to
flush out additional contaminants or it can be treated and dis-
charged. Recycling or flushing serves to accelerate the stabi-
lization of the landfill so that the system can be discontinued
at an earlier date. The three most widely used recycling methods
are: spray irrigation, overland or at-grade irrigation, and
subgrade injection or tile fields. Leachate treatment, although
effective in removing the contamination, does not help prevent
further leachate generation. Therefore methods of leachate
treatment are not detailed in this manual.
Spray irrigation has the advantage among the three of
effecting some leachate treatment during the spraying event
through both aeration and infiltration through the surface soil
layer. Spray nozzles are placed at 15- to 30-m (50- to 100-ft)
intervals on the landfill, and effluent is periodically pumped
through them onto the landfill surface.
Overland irrigation is an inexpensive, well-developed agri-
cultural technique that uses trenches, spreading basins, or gated
pipe to spread effluent. Leachate is pumped into the distribu-
tion system once or twice a week and allowed to infiltrate into
the ground. With both spray irrigation and overland irrigation,
an impermeably lined pond is necessary to provide storage of the
leachate between irrigation events.
Subgrade irrigation through a tile field or wells, although
more expensive initially than the other two, may be used con-
tinuously and has the advantage of avoiding local odor problems.
Tile field construction is similar to that of a large on-lot
sewage disposal system in that perforated pipe is buried in
gravel-lined trenches. Very large tile fields must be subdivided
into smaller units and each unit fed leachate separately. Shal-
low well injection systems are constructed similarly to well
point extraction systems (detailed in the Extraction section).
All of these systems must be designed so that the leachate
is spread evenly over the landfill. Uniform distribution of
leachate in the fill will promote uniform stabilization. The
rate of application must also be controlled so that the leachate
does not mound too high. Generally a rate of a few inches per
acre per week is adequate. If the leachate mound rises too high
in the fill, the groundwater flow direction may change and the
leachate could migrate away from the landfill. Careful design
can prevent this problem.
Costs
The capital costs of leachate spreading and application
systems range from $1,235 to $7,500 per hectare ($500 to $3,000
per acre), depending on the use of open trenches, spray irriga-
49
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tion, or buried pipe. The present worth of the three systems is
shown on Table 2.
Evaluation
Advantages—
1. Recycling accelerates stabilization of the landfill.
2. No treatment facilities are initially required for collected
leachate.
Disadvantages—
1. Initial and maintenance expenses are high.
2. Above-grade systems often create odor problems.
3. Careful management of application is required.
4. Site access must be well controlled to prevent vandalism and
accidents.
5. Leachate recycling may lead to increasing volumes of leach-
ate. As a result, handling costs may increase and leachate
may eventually have to be discharged to ground or surface
waters.
Recommendations
Leachate recycling is useful in conjunction with leachate
collection systems. Recycling is often preferable to leachate
treatment and discharge because it promotes rapid landfill
stabilization.
References
For further discussion, see references 60, 62, and 66.
50
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TABLE 2. PRESENT WORTH OF LEACHATE RECYCLING SYSTEMS*
Annual Operation Annual
Capital and Power . Present
System Costs Maintenance Costs Costs Worth Total
Spray
Irrigation 30,900
(solid set)
At-grade
Irrigation 4,600
(gated pipe,
ridge and
furrow)
Subgrade
Irrigation
(buried
pipe)
10,800
3,500
2,500
24,500 305,500 336,400
N/A 27,300 31,900
1,550
N/A 16,900 23,700
*Source: Pound, C. E., R. W. Crites, and D. A. Griffes, Costs
of Wastewater Treatment by Land Application. EPA-430/9-75-
003, June 1975, 156 pp. (reference 66).
51
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SECTION 5
CHEMICAL IMMOBILIZATION
Chemical immobilization is a developing technique used to
bind contaminants so that they cannot migrate and form leachate.
Methods of chemical immobilization rely on the initiation of a
chemical reaction which produces either a stable insoluble com-
pound from the potential contaminants, or a chemically formed
impervious membrane to stop their flow.
Chemical fixation is the application of"chemicals to destroy
or stabilize hazardous materials. This method can be used to
immobilize the in situ landfill, or the contaminant-producing
materials that have been chemically stabilized can be used as a
surface seal on the landfill.
Chemical injection is the injection of chemicals into a
landfill to immobilize or destroy a potential contaminant. This
method involves fairly sophisticated technology and is most
useful in areas where leachate formed from waste would otherwise
be extremely hazardous.
CHEMICAL FIXATION
Description
The application of chemicals to destroy or stabilize hazard-
ous materials and potential pollutants has been a common practice
for many years, particularly for industrial wastes. Generally,
chemical treatment is quite waste-specific. Thus, an effective
system in one case may be ineffective or totally inapplicable in
another. For example, the application of chlorine to destroy
cyanides, the application of lime to precipitate and insolubilize
fluorides, and the application of alkalis to precipitate and immo-
bilize heavy metals are standard but waste-specific processes.
Since the early 1970s, several proprietary processes have
been developed which tend to be applicable to a broader range of
wastes. Some of these newer systems are more applicable to
liquids and thin sludges, while others function best with heavier
sludges and solids. In any case, the processes rely on the
reactions of such materials as portland cement, lime, and common
silicates for the encapsulation, solidification, and/or cementa-
52
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tion of a waste material. It is these proprietary fixation
methods that are addressed in this section.
Each of these processes entails the mixing of the cementa-
tion/setting/reactive agents (cement, lime, silicates, etc.) with
the waste material. In the case of liquids the agent absorbs the
waste; in the case of solids the agent coats the surface of the
solids to cement them together. In sludges, where both liquids
and solids are present, both absorption and cementation (or
setting) occur. Some of these processes rely mainly on the
ability of the chemical system to insulate each particle of
pollutant from adjacent leaching fluids; others rely upon the
formation of a relatively impermeable mass to exclude leaching
fluids from passing through the waste.
The earliest commercially prominent stabilization system was
a process offered by Chemfix for application to hazardous liquids
and sludges. Stabilization processes are now offered by other
firms such as the Environmental Technology Corporation, IU Con-
version Systems, Inc., and the Dravo Corporation. The latter two
firms are primarily oriented toward the stabilization of sulfur
dioxide scrubber sludge.
The stabilization of waste materials by the addition of
chemical agents is included in this report because, in particular
instances, the process is a viable means for controlling poten-
tial pollutants. However, this process is not feasible for in ,
situ landfill problems because the success of the system is
dependent upon the intimate mixing of the chemical agents and the
material to be stabilized; without this necessary mixing, the
municipal refuse cannot be coated and encapsulated and, hence,
the normal landfill processes of degradation and leaching will
not be prevented. To ensure the mixing of the chemicals with the
refuse would require excavating the entire landfill, which would
provide little advantage over excavating and relocating the
material to an environmentally sound site.
An alternative to the application of chemical fixation
agents to the in situ landfill is the use of these agents to
stabilize waste materials for use as a cover for a problem land-
fill. After proper processing, these waste materials can be
spread, graded, and thereafter cemented into a stable, relatively
impermeable cover (see Figure 16). It may be necessary to obtain
a permit to use chemically stabilized waste materials as a land-
fill seal.
An ideal situation would be a problem landfill located near
a source of chemically stabilized waste material. The material
would be readily available and could be applied to the landfill
as a cap. The landfill surface would first have to be regraded,
as necessary to contours close to the desired final grade.
The chemically stabilized material would then be applied at an
53
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Ul
4 hectares (10acres)
Contour Grade 16 -12 percent)
Gravel Trench
Mushroom Cap
Gas Vent
Seeding and
Mulching
Max. Slope
18 percent
l2-l5m(40-SO,M)
Cap of Chemically Stabilized
Waste Material C 60m (2ft)D
Water]
Table
UNCONSOLIDATED
EARTH MATERIALS
Not to Scoff
Figure 16. Cross section of landfill sealed with
stabilized waste material.
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approximate compacted thickness of 0.6 m (2 ft), with appropriate
drainage swales to remove surface water.
As with any surface seal, provisions would have to be made
for gas venting. A gravel trench the length of the site with
mushroom cap vents at periodic intervals is one recommended
method (see Figure 16). It is recommended that the landfill be
covered with soil and revegetated (see Revegetation section).
Costs
The amount of stabilized waste material required for a
0.6-m (2-ft) cover on the 4-hectare (10-acre) landfill will total
25,460 m3 (33,300 yd3). since it is a waste material, it is
assumed that it will be available at no cost. The project costs,
then, will include: (1) site preparation, (2) handling of cover
material, and (3) spreading and grading. It is estimated that
the cost of site preparation, spreading, and grading will range
between $33,300 and $56,600.
The additional and major cost of material transportation is
dependent upon the distance and time of travel between the source
of the material and the landfill. This cost will be a function
of the type and condition of the roads and the traffic flow.
This additional cost will vary considerably, but for rough esti-
mating purposes, at a 16-km (10-mile) distance a transportation
cost of $65,000 is calculated, and at a 48-km (30-mile) distance
a cost of $135,000 is estimated.
Unit costs used in these calculations include unit cost
items 8, 9, and 10 (see Appendix).
Evaluation
Advantages—
1. The use of a waste material to cover and seal a landfill
solves two environmental problems: (1) it neutralizes a
leaching landfill and (2) it provides an environmentally
acceptable means of disposing of a waste material.
2. Compared with common cover materials, most chemically fixed
solids when properly compacted are quite impermeable.
3. The method is cost effective when the distance between the
source of the waste material and the landfill is not great.
4. Construction methods are simple.
Disadvantages—
1. Waste materials used for sealing must be tested to ensure
55
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that they will not release toxic levels of sulfates, chlo-
rides, and other pollutants.
2. Covering and sealing only prevents surface water infil-
tration and will not correct any landfill problems due to
groundwater movement.
3. Normal landfill settling will tend to break the cover and
seal and, thus, the site will require long-term maintenance.
Recommendations
Chemical fixation agents are useful in stabilizing waste
materials used to cover and seal a landfill. This method can be
used effectively in conjunction with other neutralization methods.
The application of fixation agents to stabilize in situ land-
fills however is not feasible because the intimate mixing of the
agents with the waste cannot be accomplished without excavation.
References
For further discussion, see references 69 through 77.
CHEMICAL INJECTION
Description
This process entails injecting reactive chemicals into a
landfill for the purpose of destroying or insolubilizing a
pollutant. Although this procedure merits exploration, no report
is available to date of its successful application.
Four factors restrict in situ chemical neutralization to
special circumstances. First, the injection of chemicals into a
common municipal landfill would only be temporarily effective.
Within a relatively short period of time the chemical action of
the neutralizing agent would be spent,, and normal landfill pro-
cesses would be generating new and contaminating leachate.
Therefore, in situ chemical neutralization is most applicable to
industrial waste contamination, and the remainder of this section
considers only that circumstance.
The second qualifying factor is that this process is waste-
specific. For example, free fluorides can be insolubilized by
the application of solutions containing the calcium ion; many
heavy metals can be insolubilized by the application of alkalis
and/or sulfides; free cyanide can be destroyed by the application
of a strong oxidizing agent; and hexavalent chromium can be
insolubilized by the application of a strong reducing agent.
Each industrial waste is a special case; it must also be recog-
56
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nized that many pollutants are not subject to chemical control,
whether landfilled or not.
A third limitation to the application of chemical injection
is that the source of the contamination within the landfill as
well as the plume of contamination and the concentration gradi-
ents within the plume must be well defined. This mandates an in-
depth preliminary investigation.
Yet a fourth factor to consider is whether the objectionable
material is entirely dissolved in the landfill leachate or is
present in the landfill as both a solution and a dissolving
solid. If the substances are completely dissolved, then the
application of chemicals to these substances may terminate the
pollution. However, if the material is also present in a solid
form and its solubility cannot be decreased by the application of
chemicals, then there is little probability that the'destruction
o£ the material through chemical addition can be 100 percent com-
plete. It is more likely that after the chemical application,
the normal landfill leachate will resolubilize the objectionable
material and generate additional pollution. On the other hand,
if the solubility of the material can be affected by changing the
local chemistry, then the situation could be favorable for
chemical injection.
Costs
For cost-estimating purposes we shall assume a hypothetical
case as follows:
The hypothetical 4-hectare (10-acre) landfill received a
single load of cyanide salts in fiber drums. Initial probing and
limited excavation confirms that the drums have been destroyed
and the cyanide material has dissolved. An exploratory drilling
and sampling program indicates a pollution plume as shown on
Figure 17 and detailed in Table 3.
The corrective action selected in this case involves:
a. installing 45 well points on 15-m (50-ft) centers
over the affected portion of the landfill;
b. pumping sodium hypochlorite solution into the wells
(4 at a time); and
c. conveying water from a developed well (or available
stream) to flood the landfill with the cyanide-neu-
tralizing chemical.
The corrective action is depicted in Figure 18. The costs will
be as follows (based on unit cost items 31, 32, 33, and 38 given
in the Appendix):
57
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s
(0
o
CM
Source of pollution
20m 166 ft)
Limits of pollution plume
Section number
201m (660 ft)
Figure 17. Pollution plume created by
cyanide salts located in the middle of
hypothetical landfill.
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TABLE 3. REQUIREMENTS FOR CHEMICAL TREATMENT OF
CYANIDE POLLUTION AT HYPOTHETICAL LANDFILL*
Section
No.
Volume
tm3(ft3)]
Ave. Cyanide Cone.
in Sect, (mg/liter)
Sodium Hypochlorite
Required
Total Cyanide Neutralization
inSect. [kg(lb)] [liters(gal)]
en
1 5,490 { 196,020)
2 16,470 ( 588,060)
3 27,440 ( 980,100)
4 38,420 (1,372,140)
5 49,400 (1,764,180)
137,220 (4,900,500)
200.0
50.0
13.0
3.1
0.78
320 ( 705)
240 ( 528)
104 ( 230)
35 ( 77)
12 ( 26)
711 (1,566)
21,773 ( 5,753)
16,305 ( 4,308)
7,086 ( 1,872)
2,363 ( 624)
789 ( 209)
48,316 (12,766)
Calculations based on landfill at density of 640 kg/m3 (40 Ib/ft ) and 45 percent
moisture (cyanide in solution in the moisture); available chlorine of 0.15 kg/liter
(1.25 Ib/gal) of sodium hypochlorite; chemical application rate of 68.09 liters/kg
(8.16 gal/lb) cyanide (150 percent of theoretical).
-------
Metering pump
4 hectares (lOacres)
Hypochlonte
storage
l2-l5ml40-50,ft)
Injection pipe is pulled
up and chemical is injected
at successive depths.
Water supply well
UNCONSOLIDATED EARTH MATERIALS
Stream
BEDROCK
Not to Seal*
Figure 18. Cross section of landfill treated by
chemical injection.
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Exploratory probing, excavation, and
drilling $15,000
Development of water supply well,
27 m (90 ft); pump and piping 5,000
Installation of 45 well points 10,100
Cost of chemical feed pump 2,200
Cost of chemical 5,400
Labor for chemical injection, raising of
well points to flood successive eleva-
tions (assumed 4 wells handled simul-
taneously) , and general labor (1,600
hours) 48,000
Power (assumed electrical supply available 500
$86,300
Evaluation
Advantages—
1. When the chemistry and circumstances are such that a hazard-
ous material is amenable to chemical control, chemical
injection may be a cost-effective method to correct a prob-
lem due to leaching.
2. The method could potentially control a hazardous situation
in which no other alternative is feasible.
Disadvantages—
1. The fact that the source of the problem is buried deeply in
the ground introduces many uncertainties such as the dimen-
sions of the affected landfill volume, the concentration
gradients in the system, whether any causative material
is retained in drums only to continue to propagate the
problem, etc.
2. Some displacement of the pollutant, perhaps to environs
outside of the landfill, will occur due to the injection
of the added volume of the chemical solution.
3. It would be difficult to measure the degree of effectiveness
of this method.
Recommendations
Chemical injection is limited in application for landfill
neutralization. However, when a known industrial pollutant is
entirely dissolved in a landfill and its location or the location
of its origin is well defined, this method could be effective in
controlling pollution.
References
For further discussion, see reference 78.
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SECTION 6
EXCAVATION AND REBURIAL
Description
The excavation and reburial of a landfill involves digging
up the existing material, loading and transporting the waste to
another site, and reburying it in accordance with accepted pro-
cedures. Before implementation of this technique, it must be
established that the new site has better attenuation and pollu-
tion-controlling characteristics than the old site. A well-
engineered existing landfill could be used to receive the waste
or, for a particularly serious pollution problem, a new site
could be designed.
It is recommended that a new reburial site be:
located in slowly permeable materials or artificially
lined to provide for-leachate attenuation or collection
and treatment;
located at least as far above the water table as the
depth of landfill, i.e., allowing 0.3 m (1 ft) of
unsaturated low-permeability material for each 0.3 m
(1 ft) of refuse deposited;
located away from all public water supplies whether
provided by surface or groundwater;
engineered to provide for diversion of surface water,
to promote surface drainage, and to include a low-
permeability cover for sealing as described in the
Surface Sealing section.
The composition of the wastes buried at the unsuitable site
must be determined before equipment and procedures can be selec-
ted for excavating the waste. An investigation should be con-
ducted by reviewing old records, digging test pits, and/or power
augering. If it is determined that the landfill contains only
municipal refuse, bulldozers, front-end loaders, and wheel-
scrapers can be used for the excavation. For landfills that bury
mixed solid wastes, additional equipment such as cranes fixed
with large-materials-handling clamshell buckets, power shovels,
62
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pull shovels, and crawler-type front-end loaders will be re-
quired. Dump trucks and rock-bodied vehicles can be used for
transport.
Typical mixed wastes might include highway guard fence
cable, railroad ties, bales of rags, large pieces of broken
concrete, bed springs, rugs, drums of used oil and tar, auto
bodies, large household appliances, asphalt pavement, paper,
cardboard, garbage, tin cans, wire, tires, etc.
Excavation and reburial projects are often plagued by prob-
lems such as birds, rodents, flies, mosquitos, odors, blowing
litter, wastes leaking during transport, and unanticipated types
or depths of refuse. In one case recently, 9 m (30 ft) of refuse
were to be excavated and removed; however, when this depth was
reached, an additional 6 m (20 ft) of uncharted.waste, limekilns,
and buildings were discovered and had to be excavated.
Costs
The following costs are developed assuming the removal of
the 4-hectare (10-acre) landfill, with depths of refuse between
12 and 15 m (40 and 50 ft), and transportation to a landfill
32 km (20 miles) distant. The assumption is also made that the
receiving landfill is a permitted site and that no special prep-
aration will be required. This example assumes dumping will be
free of charge. Daily and final cover will be the responsibility
of the receiving landfill. " ~^~
Based on these assumptions, the cost to excavate, transport,
and rebury the existing landfill [428,000 m3 (560,000 yd3)] will
range between $3,495,000 and $5,645,000 for the hypothetical
case.
The unit costs used in these calculations include items 7,
8, and 9 (see Appendix).
Evaluation
Advantages--
1. The source of contaminants is removed.
2. The wastes can be reburied in a controlled sanitary land-
fill, and the new site can be engineered to prevent environ-
mental degradation.
3. The final land configuration of the original site can be
designed to serve a useful purpose (e.g., a body of water
could be created in the excavated landfill for recreation).
4. For excavated landfills over 10 years old, the fresh refuse
would be on the bottom of the reburial site where it can
63
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age, and the decomposed refuse would be on the top; there-
fore odor and vector problems would be minimized at the new
site, and in some cases the decomposed refuse could be used
as cover material.
Disadvantages—
1. Acceptable burial sites may be located long distances from
the original site, in which case transportation could be
costly. The condition of the haul roads, means of pre-
venting leaky loads, and the accessibility of both sites are
also important.
2. There may be political, social, and economic restraints to
finding an acceptable reburial site. Restraints by govern-
mental agencies are also a major consideration.
3. Excavation itself is difficult and often complicated by
unwieldy materials and bulky or weighty demolition wastes.
4. There is a possibility of encountering hazardous wastes not
documented (e.g., containerized volatile substances, pesti-
cides, industrial process wastes, and pathogenic wastes).
5. If the landfill extends below groundwater, wet excavation
will be involved and provisions must be made for disposition
of the contaminated groundwater.
6. Nuisances and vectors must be controlled during excavation.
7. Reclamation of the excavated site will be necessary.
The excavation and reburial process can be a viable method
of removing a polluting landfill if proper precautions are taken
to control nuisances and vectors. Where the excavated waste must
be hauled great distances [in excess of 48 km (30 miles)], trans-
portation costs will be significant. Another cost factor which
could be important is the preparation of the new landfill to
receive the excavated wastes. Land acquisition for a new land-
fill in the vicinity may be difficult in terms of political
and/or social opposition and monetary obstacles.
Recommendations
Excavation and reburial should be considered as a last
resort since it is an extremely expensive and difficult proce-
dure. There are, however, cases in which either the hazard of
contamination is so severe or the water resources to be protected
are so valuable that this method would be recommended.
REFERENCES
For further discussion, see references 78 through 82.
64
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SECTION 7
SUMMARY
To minimize pollution from a solid waste disposal site,
leachate generation and movement must be limited or controlled.
Leachate production can be controlled by minimizing the amount of
water entering the landfill. Reducing the amount of water in
contact with the fill reduces the quantity of leachate generated.
However, if the quantity of water is not sufficiently minimized,
the pollutional load may not be reduced at all and, indeed, may
be increased due to higher contaminant concentrations. There-
fore, if water inflow reduction is to be used in landfill neu-
tralization, the reduction must be significant.
It is generally not possible to reduce or eliminate the
amount of moisture present in municipal refuse when collected.
However, both vertical and horizontal percolation into the fill.
can be controlled by a- number of techniques designed to either
increase or decrease flow. The techniques considered herein have
been grouped in five categories: surface water control, ground-
water control, plume management, chemical immobilization, and
excavation and reburial. It may be necessary to apply more than
one method from more than one category to effect significant
results. For ease of comparison, the major characteristics and
estimated costs of these measures are summarized in Table 4.
SURFACE WATER CONTROL
Surface water infiltration can often be reduced during
normal landfill closure if careful design and construction prac-
tices are followed. There are four ways to minimize water infil-
tration. The first is to increase runoff from the landfill
surface by regrading to provide for moderate sheet flow from the
surface. The second is to reduce the amount of runoff flowing
onto the landfill surface by constructing diversion ditches and
terraces. The third is to decrease infiltration into the land-
fill by applying a low permeability cover or seal to retard the
vertical movement of water below the cover material. The fourth
is to increase interception and transpiration of precipitation by
planting vegetation on the landfill.
To increase runoff from the landfill by regrading, the
surface should be sloped such that the water has the shortest
65
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TABLE 4. SUMMARY OF ESTIMATED COSTS
AND CHARACTERISTICS OF REMEDIAL METHODS
Method
Average
Estimated Costs*
($ in Thousands)
Characteristics/Remarks
Contour Grading 184
Surface Water Diversion 20
Surface Sealing
Clay [15-46 cm (6-18 in.)] 234
Bituminous Concrete [4-13 cm
(1.5-5 in.)] 315
Fly Ash [30-60 cm (12-24 in.)] 235
PVC (30 mil) 482
Drainage Field (if required) 65
Revegetation on Slopes<12 percent 10
on Slopes>12 percent 19
Surface Water Control
Increases runoff, reduces infiltration.
Diverts surface water from fill.
If locally available, native clay is eco-
nomical means of retarding infiltration.
Rapid coverage; can eliminate infiltration.
Material may leach metals; may be available
free.
Very impermeable; expensive seal; careful
subgrade preparation is necessary.
Carries infiltrated water off seal; in-
creases effectiveness of seal.
Stabilizes cover material; seasonally in-
creases transpiration; provides aesthetic
benefit.
Bentonite Slurry Trench
Grout Curtain
Sheet Piling
Bottom Sealing
670
1,400
800
4,000
Groundwater Control
Simple construction methods; retards ground-
water flow.
Very effective in permeable soils.
Widely used for shoring.
Leachate collection may be needed; acts as a
liner; difficult drilling through refuse.
Drains 23
Well Point Dewatering 185
Deep Well Dewatering 183
Injection/Extraction Barrier 199
Spray Irrigation 336
At-grade Irrigation 32
Plume Management**
Effective in lowering water table a few
meters in unconsolidated materials; can
be used to collect shallow leachate.
Suction lift limits depth to 7-9 m (20-30
ft); inexpensive installation; uses only
one pump; can be used to collect shallow
leachate.
Used in lowering deep water tables; one
pump needed per well; high maintenance
costs.
Creates a hydraulic barrier to stop leach-
ate movement; operation and maintenance
costs are high.
Spreads leachate over the landfill for re-
cycling; potential odor problem.
Gated pipe with ridge and furrow irriga-
tion; potential odor problem; recycles
leachate.
Subgrade Irrigation 28
Chemical Fixation of Cover 145
Chemical Injection 86
Excavation and Reburial 4,570
Large-scale drainage field; recycles leach-
ate.
Chemical Immobilization
Uses chemically fixed sludge to provide a
top seal; provides means of disposal for
sludge; he?.ps stabilize landfill.
Immobilizes a single pollutant; in most
cases not feasible.
Excavation and Reburial
Very expensive; difficult construction.
•Costs for hypothetical 4-hectare (10-acre) landfill (see Figure 1). High and low estimates
were averaged to determine these costs.
*'Costs include present worth of 20 years, operation, maintenance, and, where applicable,
power for 4-hectare (10-acre) landfill.
66
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possible flow path from any point on the site. Thus a mound in
the central portion sloping equally on all sides is an ideal
regrading plan. Depending on the type of soil on the site,
slopes of 6 to 12 percent are generally recommended. The cost of
this regrading will depend upon the current grade of the landfill
and the availability of local cover material. If major changes
in grade are necessary, costs will escalate rapidly.
Diversion ditches are generally most useful in areas where
the landfill is at the middle or the bottom of a slope and sur-
face water collects upslope from the landfill and flows onto it.
Standard construction techniques developed for handling storm
runoff in highway and subdivision construction can be used to
redirect surface water around a landfill. These techniques are
generally not excessive in cost if the equipment used for re-
grading and covering operations is already available at the
landfill.
If the material available for covering the site is highly
permeable and if the landfill is in an area of high rainfall,
surface sealing may be effective. A number of materials poten-
tially suitable for sealing, in order of generally increasing
costs, are local clay (where available), bentonite, bituminous
concrete, asphalt, and plastic (PVC) membranes. These materials
can markedly reduce infiltration into the landfill. In cases
where low permeability,_c.pyer material is to be placed over the__
seal, it may be necessary to construct a drain on top of the seal
to carry away water intercepted by it. A properly constructed
seal can reduce infiltration essentially 100 percent.
Revegetation of the completed landfill surface is recom- '
mended in favorable climates to stabilize the final cover mate-
rial, aesthetically upgrade the area, and seasonally increase
evapotranspiration of precipitation. Procedures for vegetating
the landfill surface are very similar to those used in stabi-
lizing highway grades and other areas of recent construction.
The surface can be hydroseeded with a suitable grass mixture and
mulched with a straw mulch. Steep slopes can be treated with
legumes or vetch to hasten stabilization. Overland runoff over
unvegetated soils rapidly erodes most cover materials and de-
stroys the final grade. Therefore, vegetation is strongly
recommended in most areas.
GROUNDWATER CONTROL
Subsurface infiltration barriers, or passive groundwater
control measures, are designed to either prevent groundwater from
flowing through the landfill and generating leachate or control
the movement of leachate away from the landfill. Barriers are
constructed of low permeability materials to divert and impede
groundwater flow in the vicinity of the landfill. The engi-
neering technology associated with groundwater barriers has been
67
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developed for use in constructing cutoff walls around and under
dams and excavation control structures in areas of shallow
groundwater, e.g., at the sea coast. Barriers that can be used
at landfills include slurry trenches, grout curtains, sheet
pilings, and landfill bottom sealing.
Slurry trenches are constructed by excavating a trench
through a bentonite slurry using draglines. The bentonite
slurry is continuously pumped into the excavation and serves to
stabilize the nearly vertical wall of the trench and ultimately
to seal the area. The excavation is often carried to bedrock or
other low permeability layer but can be terminated at shallower
depths. Although costly, slurry trenches are generally the least
expensive form of passive groundwater barrier.
Grout curtains are emplaced by forcing a thin cement grout
through tubes which are driven deep into the ground on 2- to 3-
foot centers and withdrawn slowly. Two or more rows of grout are
usually needed to provide a seal. Like a slurry trench, the
grout is generally emplaced down to an impermeable layer. Grout
curtains are quite expensive when constructed to the dimensions
necessary to cut off groundwater flow in the vicinity of a
reasonably sized landfill.
Sheet piling has been extensively used in near-shore and
offshore construction to stabilize areas for excavation. It is
driven into- the ground -with—a—pile—d-river— so—that-depending on
the design the piles either butt or interlock. For sheet piling,
as for all of the passive groundwater barriers, unconsolidated
material must be present around the landfill with no large stones
or boulders as these will deflect or prevent the piling from
being effectively driven. Sheet piling is generally very expen-
sive when used in the quantities necessary at landfills.
Bottom sealing of a landfill is like emplacing a grout
curtain in a bowl shape under the landfill. Grout tubes are
driven through the landfill, which can entail considerable
expense because of bulky or resistant refuse. A bottom-grouted
landfill would be similar to an engineered landfill with a liner
except that the seal would be emplaced after filling. Generally
speaking, unless the sources of leachate generation were removed,
leachate collection would be necessary with a bottom-grouted
landfill.
PLUME MANAGEMENT
The purpose of plume management or active groundwater
management is to manipulate the water table in the area of the
landfill to either prevent the formation of leachate or contain
its spread. To do this, water must be extracted from or added to
the groundwater system through drains, shallow well points, or
deep wells. The capital costs of these systems are generally
68
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much lower than those of passive barriers, but the operation and
maintenance costs are considerably higher since in most cases a
continuing supply of electrical power and ongoing maintenance of
pumps and wells is required.
The technology of drains has been developed for use in
agriculture, highway, and construction. Drains can be a low-cost
means of lowering the water table a few meters provided the area
in which the drain is to be emplaced can be readily excavated.
Drains can be used to lower the.water table upgradient of the
fill, to collect leachate if it is following a shallow flow path,
or to introduce leachate over the refuse on top of the fill.
Drains are generally constructed using crushed stone and perfo-
rated pipe. Construction costs are comparatively low providing
the depth of drain emplacement is not excessive. However, when
highly mineralized waters are present, drains are more suscep-
tible to clogging and maintenance costs may be significant.
Well points are widely used in construction to dewater
shallow excavations. They are effective up to the limits of
suction lift, i.e., 7 to 9 m (20 to 30 ft) below the ground. The
main advantage of well points is that a large number of wells can
be powered using a single suction pump. They are effective for
dewatering shallow landfills and collecting shallow leachate.
The installation cost for well points is moderate but maintenance
can be relatively high since a good vacuum must be maintained on
the entire system.
Deep wells can be used to dewater consolidated formations or
areas where the water table is too deep for economical use of
suction lifts or drains. Construction and operation of deep
wells is a relatively simple but long-term operation, and main-
tenance costs can be high especially if the wells are used to
collect leachate.
Any of these systems can be used to inject water into an
aquifer to provide a groundwater barrier to the flow of leachate.
This technology has been developed and applied in controlling the
spread of sea water into potable aquifers and is potentially
applicable to control leachate movement toward important well
fields. However, the operation and maintenance costs are. high
and the leachate is only rerouted from its path, the quantity
generated is not reduced.
The use of any of these systems for leachate collection will
necessitate some means of leachate disposal. It is often feasi-
ble to recycle the leachate onto the landfill to hasten landfill
stabilization. Leachate can be recycled by spray irrigation, at-
grade irrigation, or subgrade irrigation (i.e., drains and tile
fields). Spray irrigation involves the highest capital, energy,
and maintenance costs, but also provides some leachate treatment
and recycling. At-grade irrigation considerably reduces the
69
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power requirements but shares with spray irrigation potential
odor problems. Subgrade irrigation provides little direct
leachate renovation but avoids the potential problem of having
large quantities of leachate exposed at the ground surface.
Generally speaking, landfills will stabilize more rapidly with
leachate recycling. Potentially, a leachate collection system
could be abandoned when the landfill has stabilized.
All of these groundwater management schemes involve a long-
term commitment of manpower and funds to the maintenance and
operation of the systems. Probably the least operation and
maintenance costs would be required using drains and the most
using a leachate collection and recycling system. However, there
may be cases where any or all of these measures will be appli-
cable and necessary for leachate control.
CHEMICAL IMMOBILIZATION
Chemical immobilization is a developing technology used to
stabilize the waste and/or cover material through a chemical
reaction. The method involves either the emplacement of a
chemically stabilized low permeability cover or the injection of
a chemical into the refuse and leachate plume to destroy a con-
taminant. The technology for chemical immobilization originated
in chemical engineering and sludge stabilization'work.
The first use of chemical immobilisation is identical—in
intent to top sealing but uses a chemically stabilized waste
product, i.e., sludge, to form a low permeability blanket on top
of the landfill. In areas where this would be permitted, this
method would have the beneficial effect of disposing of a waste
product and at the same time aiding in the stabilization of the
landfill. Most chemical immobilization processes are proprie-
tary, but in general they involve either a cement base or chemi-
cal reaction base process. When a suitable waste material is
available within reasonable distance of the landfill, this pro-
cedure can be cost-advantageous over other top sealing tech-
nology.
The other form of chemical immobilization is the injection
of a chemical to destroy or tie up a specific pollutant. Gener-
ally speaking, any one chemical is effective only against one or
two types of pollutants. This process is potentially very expen-
sive but would be applicable in areas where a known hazardous
material, such as cyanide, had been emplaced and was migrating
with the groundwater. Chemical immobilization is a developing
field and, at present, most methods of chemical immobilization
would not be feasible for municipal refuse.
EXCAVATION AND REBURIAL
The purpose of excavation and reburial is to move the
70
-------
leachate-generating material to a better engineered or environ-
mentally less sensitive area. Although conceptually very simple,
excavation and reburial is expensive as well as practically and
politically difficult. Basically, the process involves removing
the entire contents of the landfill with common construction
procedures and moving them, usually by truck, to another area
where a better engineered and sited landfill is available.
Problems arising in excavation and reburial include the technical
problems of removing large quantities of bulky and partially
decomposed wastes from the landfill, transporting partially
saturated and saturated material over public roads without
spillage or leakage, and cleaning up a leachate-filled pit after
the waste material has been removed.
In addition, in most cases there are political constraints
on the movement of such material through any populated areas, and
there may be considerable local opposition to the importation of
municipal refuse to an existing or new landfill. The process is
in any case very costly, but in areas where a severe leachate
problem has developed and a properly designed landfill is avail-
able nearby it may be applicable.
In summary, we believe that surface regrading and revegeta-
at practically all landfills
and that surface sealing will be a useful adjunct to this where
no natural low permeability cover is available. Groundwater
manipulation is potentially very effective in areas where either
much of the landfill is below the water table or the leachate is
moving toward an important public water supply. Leachate collec-
tion and recycling may be a useful part of groundwater control.
Chemical immobilization is a relatively new technology whose
applicability will increase as more techniques are developed;
however, the use of a stabilized sludge or other waste product
for cover or sealing material appears to be feasible in areas
where it would not be prohibited by local authorities and where
the material is locally available. Excavation and reburial
should be generally considered as a last resort which would be
used only when all efforts to stabilize the refuse in place
appear to be futile. Although it is potentially very effective
it is also a difficult and expensive undertaking.
In the selection of remedial measures for use in minimizing
pollution at any waste disposal site, professional feasibility
assessment and design will be necessary.
71
-------
REFERENCES
1. U.S. Department of Interior. Bureau of Reclamation. Earth'
Manual. First Ed., U.S. Government Printing Office, Wash-
ington, D.C., 1960. 751 pp.
2. U.S. Department of Agriculture. Soil Conservation Service.
Soil Survey for Montgomery County. Pennsylvania, April
1967. 187 pp.
3. American Association of State Highway Officials. A Policy
on Landscape Development for the National System of Inter-
state and Defense Highways. Washington, D.C., 1961. 38 pp.
4. Erosion and Sediment Control: Surface Mining in the Eastern
U.S.—Planning. EPA -625/3-76-006, U.S. Environmental Pro-
tection Agency, Washington, D.C., Oct. 1976. 102 pp.
5. Erosion and Sediment Control: Surface Mining in the Eastern
U. S-.-^=--De-sig_n..., EPA -625/3-76-006, U.S. Environmental Pro-
tection Agency, Washington," D.C. , Oct. 1976. 136 pp.
6. U.S. Department of Agriculture. Soil Conservation Service.
Standards and Specifications for Soil Erosion and Sediment
Control in Developing Areas. College Park, Maryland,
July 1975.
7. Flower, F. B. and I. A. Leone. Damage to Vegetation by
Landfill Gases. The Shade Tree, 50 (6.6):61-72.
8. Flower, F. B., et al. Vegetation Kills in Landfill Environs,
EPA-600/9-77-026, U.S. Environmental Protection Agency, Cin-
cinnati, Ohio, Sept. 1977.
9. Leone, I. A., et al. Damage to Woody Species by Anaerobic
Landfill Gases. J. Arboriculture. 3(12):221-225.
10. Leone, I. A., et al. Damage to New Jersey Crops by Landfill
Gases. Prepared for U.S. Environmental Protection Agency,
Solid and Hazardous Waste Division, Grant #R80 3762-02,
April 1977.
11. Reindl, J. Solid Wastes Disposal Depends on Landfill Tech-
niques. Solid Waste Management, June 1977, p. 22. (Uni-
versity of Wisconsin Ext., Landfill Course Lesson #3.)
72
-------
12. Reindl, J. Managing Gas and Leachate Production on Land-
fills. Solid Waste Management, July 1977, p. 30. (Uni-
versity of Wisconsin Ext., Landfill Course Lesson #4.)
13. The Asphalt Institute. Asphalt for Water Control and En-
vironmental Preservation. Information Series No. 164(15-
164), Dec. 1973. 17 pp.
14. Marks, B. D., and T. A. Haliburton. Acceleration of Lime-
Clay Reactions with Salt. J. Soil Mech. Found. Div. ,
ASCE, Vol. 98, No. SM4, Proc. Paper 8827, April 1972.
pp. 327-339.
15. Soil-Cement Construction Handbook. Portland Cement Asso-
ciation, Chicago, Illinois, 1956.
16. Pennsylvania Department of Transportation. General Spe-
cifications for Lime Subgrade Stabilization. St. Davids,
Pennsylvania, 1974.
17. Interagency Engineering Committee. Soil Aggregate
Gradations and Descriptions, New Jersey, undated.
18. Pennsylvania Department of Transportation. From 408:
Specifications.. Sections 332 and 333, Harrisburg, Penn-
sylvania, 19-7.6-.. —__.,,
19. What's New in Landfill Liners. The American City & County,
Feb. 1977. pp. 54-56.
20. Phillips Petroleum Company. Petromat Liners. Bartlesville,
Oklahoma. 30 pp.
21. Haxo, H. E., Jr., and R. M. White. Evaluation of Liner
Materials Exposed to Leachate. EPA-600/2-76-255, U.S.
Environmental Protection Agency, Cincinnati, Ohio, Sept.
1976. 54 pp.
22. Swope, G. Survey of Revegetation on Sanitary Landfills.
Unpublished M.S. Thesis, Pennsylvania State University,
1972.
23. Pennsylvania State University. Agronomy Guide, 1972-
1978. State College, Pennsylvania, 1977. pp. 45-47.
24. Flowers, F. B. Environmental Impact of Landfill Gas.
University of Wisconsin Ext., Rutgers University, New
Brunswick, New Jersey, 1976. 5 pp.
25. Blaney, H. F. Water and Our Crops. In: Water - The
Yearbook of Agriculture. U.S. Department of Agriculture,
Washington, D.C. 1955.
73
-------
26. Blaney, H. F. Monthly Consumptive Use Requirements for
Irrigated Crops. In: Proceedings ASCE - Irrigation and
Drainage Division, Vol. 84, No. IRI, 1959.
27. Rosenberg, N. J. , H. E. Hartand, and K. W. Brown. Evapo-
transpiration - Review of Research. MP 20, Agr. Exper.
Sta., University of Nebraska, Lincoln, Nebraska, 1968.
28. Molz, F. J., S. R. VanFleet, and V. D. Browning. Trans-
piration Drying of .Sanitary Landfills. Groundwater,
12(6):391-98, 1974.
29. Molz, F. J. Discussion of Transpiration Drying of Sanitary
Landfills. Groundwater, 13(5):451, 1975.
30. Ham, R. K., and R. Kranauskas. Leachate Production from
Milled and Unprocessed Refuse. University of Wisconsin
Ext., 1975. 14 pp.
31. U.S. Department of Agriculture. Grass - The Yearbook of
Agriculture. Washington, D.C., 1948. 892 pp.
32. Neumann, V. Possibilities of Recultivation of Refuse Dumps.
Muell and .Abfall, 3(1):5-18, Jan. 1971.
33. -UL..S. Department of Agriculture^__Land__^_The Yearbook of
Agriculture. Washington, D.C., 1958. 605 pp.
34. U.S. Department of Agriculture. Crops in Peace and War -
The Yearbook of Agriculture. Washington, D.C., 1950-51.
942 pp.
35. Krynine, D. P., and W. R. Judd. Principles of Engineering
Geology and Geotechnics. McGraw-Hill Book Co., New York,
1957. 730 pp.
36. Tschebotarioff, G. P. Soil Mechanics Foundations and Earth
Structures. McGraw-Hill Book Co., New York, 1951. 655 pp.
37. Field and Office Manual. Engineering News-Record, New York,
1965. 128 pp.
38. Lenahan, T. There Is a Place for Grouting in Underground
Storage Caverns. Bull. Assoc. Engr. Geol., 10(2):137-44,
1973.
39. Kapp, M. S. Slurry-trench Construction .for Basement Wall of
World Trade Center. Civil Engineering, 'ASCE, April 1969.
pp. 36-40.
74
-------
40. American Colloid Company. Volclay Product Literature. Nos.
229-M, 230-G, 270-A, 280-A, Skokie, Illinois, 1972.
41. Applied Nucleonics Company, Inc. Technical Information
Summary: Soil Grouting. Prepared for U.S. Environmental
Protection Agency, Dec. 1976. 15 pp.
42. Gerwick, B. C., Jr. Slurry-trench Techniques for Diaphragm
Walls in Deep Foundation Construction. Civil Engineering,
ASCE, Dec. 1967. pp. 70-72.
•
43. Bentonite Slurry Stabilizes Trench, Keeps Groundwater Out.
In: Field and Office Manual. Engineering News-Record, New
York, 1965. pp. 70-73.
44. Calcium Bentonite Slurry Seals Canal. In: Field and Office
Manual. Engineering News-Record, New York, 1965. p. 55.
45. Toronto's Cover-Then-Cut Subway. In: Field and Office
Manual. Engineering News-Record, New York, 1965. p. 52.
46. American Colloid Company. Use of Bentonite as a Soil Sealant
for Leachate Control in Sanitary Landfills. Data 280-E,
Skokie, Illinois, Sept. 1975. 36 pp.
47. Raymond Internationa-1, Inc. Siroc Grout Technical Manual.
New-York, 1967.
48. American Cyanamid Company. All About Cyanamid AM-9 Chemical
Grout. Wayne, New Jersey, 1975. 95 pp.
49. Karol, R. H. Chemical Grouting Technology. J. Soil Mech.
Found. Div., ASCE, Vol. 94, No. SMI, Proc. Paper 5748,
Jan. 1968. pp. 175-204.
50. Halliburton Services. Grouting in Soils, Vol 2. Design and
Operations Manual. PB-259044, U.S. Department of Commerce,
NTIS, Springfield, Virginia, June 1976.
51. Revised Bibliography on Chemical Grouting. Third Progress
Report of the Committee on Grouting, W. K. Seaman, Chmn.
J. Soil Mech. Found. Div., ASCE, Vol. 92, No. SM6, Proc.
Paper 4469, Nov. 1966. pp. 39-66.
52. U.S. Steel. U.S. Steel Sheet Piling: Design Extracts from
Former Catalogs. Adv.-18605-52, Reprinted from Carnegie
Steel Sheet Piling, Pittsburgh, Pennsylvania.
53. Bethlehem Steel Co. Bethlehem Steel Sheet Piling: Manufac-
turer's Catalogs. SPECDATA, Folders 2790, 2570, May 1971.
75
-------
54. Bethlehem Steel Co. Steel Sheet Piling. Catalog 2620,
Bethlehem, Pennsylvania, Oct. 1970.
55. U.S. Steel. Hot Rolled Steel Shapes and Plates, July 1963.
56. Bethlehem Steel Co. Bethlehem Structural Shapes. Catalog
S-58-A.
57. Stubbs, F. W., Jr., Ed. Handbook of Heavy Construction.
McGraw-Hill Book Co., New" York, 1959.
58. Armco Drainage & Metal Products, Inc. Handbook of Drainage
and Construction Products. The Lakeside Press, Chicago,
Illinois, 1958.
59. Todd, D. K. Ground Water Hydrology. John Wiley & Sons,
Inc., New York, 1959.
60. Dominico, P. A. Concepts and Models in Ground Water Hydrol-
ogy. McGraw-Hill Book Co., New York, 1972.
61. The Johnson Division, University of Pennsylvania. Ground
Water and Wells. Universal Oil Products Co., St. Paul,
Minnesota, 1966. pp. 286-94.
62. Harr, M. E. Groundwater and Seepage. McGraw-Hill Book Co.,
New York, -1962.
63. Amar, A. L. Theory of Ground Water Recharge for a Strip
Basin. Groundwater, 13 (3)-.282-93, 1975.
64. Gregg, D. 0. Protective Pumping to Reduce Aquifer Pollution.
Glynn County, Louisiana. Groundwater, 9(5), 1971.
65. Nobel, D. G. Well Points for Dewatering. Groundwater, 1(3):
21-36, 1963.
66. Pound, C. E., R. W. Crites, and D. A. Griffes. Costs of
Wastewater Treatment by Land Application. EPA-430/9-75-003,
June 1975. 156 pp.
67. The Asphalt Institute. Drainage of Asphalt Pavement Struc-
tures. College Park, Maryland, Manual Series No. 15 (MS-15),
May 1966.
68. Shehan, N. T. Injection/Extraction Well System - A Unique
Seawater Intrusion Barrier. Groundwater, 15(1):32-51, 1977.
69. IU Conversion Systems, Inc. Poz-O-Tec, Poz-O-Pac, and Poz-
0-Soil Product Literature. Philadelphia, Pennsylvania.
76
-------
70. Mullen, H., L. Ruggiano, and S. I. Taub. The Physical and
Environmental Properties of Poz-O-Tec. Engineering Founda-
tion Conference on Disposal of Flue Gas Desulphurization on
Solids, Hueston Woods State Park, Ohio, Oct. 1976.
71. Taub, S. I. Treatment of Concentrated Wastewater to Produce
Landfill Material. Presented at Int. Poll. Engr. Exp. .
Congr., Anaheim, California, Nov. 1976.
72. Mullen, H., and S. I. Taub. Tracing Leachate from Landfills
- A Conceptual Approach. Presented at the National Confer-
ence on Disposal of Residues on Land, St. Louis, Missouri,
Sept. 1976.
73. IU Conversion Systems, Inc. Poz-O-Tec Process for Econom-
ical and Environmentally Acceptable Stabilization of Scrub-
ber Sludge and Ash. Philadelphia, Pennsylvania.
74. Freas, R. C. The Stabilization and Disposal of Scrubber
Sludges - The Dravo Process. American Petroleum Institute
Committee on Refinery Environmental Control, Salt Lake
City, Utah, Sept. 1975.
75. Hoffman, D. C. Calcilox - An Alternative to Slurry Waste
Disposal Sites. Draft Report, U.S. Environmental Protec-
tion Agency, 1977. p. 36.
76. Snyder, G. A., and D. C. Hoffman. Effective Disposal of
Fine Coal Refuse Using Calcilox Stabilization. Dravo Lime
Company, Pittsburgh, Pennsylvania.
77. Conner, J. R. Ultimate Disposal of Liquid Wastes by Chemi-
cal Fixation. Presented at the 29th Annual Purdue Industrial
Waste Conference, West Lafayette, Louisiana, May 1974.
78. Farb, D. G. Remedial Approaches for Upgrading Hazardous
Waste Disposal Sites. Draft Report, U.S. Environmental
Protection Agency, 1977. p. 36.
79. Sanitary Landfill Design and Operation. SW-651s, U.S. En-
vironmental Protection Agency, Washington, D.C., 1972.
59 pp.
80. Kellogg, F. H. Construction Methods and Machinery. Prentice-
Hall, Inc., New York, 1954.
81. Roy F. Weston, Inc. Leachate Control Strategies for Llangol-
len Landfill. Preliminary Feasibility Study, West Chester,
Pennsylvania, May 1974. pp. 57-59.
82. Roy F. Weston, Inc. New Castle County, Delaware Department
of Public Works, Llangollen Landfill Rehabilitation Project.
Recommended Plan. West Chester, Pennsylvania. 7 pp.
77
-------
UNIT COSTS
USED AS BASIS FOR
COST ESTIMATES*
oo
Item
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Item
Unclassified excavation**
Borrow excavation, earth**
Borrow excavation, rock**
Diversion ditch/channel excavation**
Trench excavation**
0-7.6 m (0-25 ft)
Trench excavation**
0-24 m (0-80 ft)
Classified excavation - solid waste**
Materials hauling
first 32 km (20 miles)
Materials hauling
additional cost over 32 km (20 miles)
Range in
Dollars/Unit
1.50 -
2.00 -
10.00 -
6.00 -
12.00 -
15.00 -
4.00 -
3.50/yd3
4.00/yd3
18.00/yd3
9.00/yd3
18.00/yd3
30.00/yd3
7.00/yd3
0.16 - 0.22/
ton-mile
0.07 - 0.12/
ton-mile
2.00 -
2.60 -
13.00 -
7.80 -
15.60 -
19.50 -
5.20 -
4 . 50/m3
5.20/m3
23.40/m3
11.70/m3
23.40/m3
39.00/m3
9.10/m3
APPENDIX
0.24 - 0.32/
tonne-km
0.10 - 0.18/
tonne-km
* These unit costs are based on rates established in the Philadelphia Metropolitan area
as of June 1977.
**Complete in place.
-continued-
-------
UNIT COSTS
USED AS BASIS FOR
COST ESTIMATES
(Continued)
VD
Item
No.
10.
11.
12.
13.
14.
15.
16.
17.
18.
Item
Fly ash and/or sludge spreading,
grading, and rolling
Native clay material**
Bentonite (FOB Philadelphia, PA)
Bentonite slurry**
1053 kg/m3 (65 lb/ft3)
Portland cement grout**
Structural concrete**
Plain cement concrete pavement**
15-cm (6-in. ) depth
Reinforced cement concrete pavement**
15-cm (6-in.) depth
Bituminous concrete pavement**
4-cm (1.5- in.) depth
on 15-cm (6-in. ) base course
Range in
Dollars/Unit
1.
2.
65.
0.
4.
125.
6.
8.
3.
on -
50 -
00 -
60 -
00 -
00 -
00 -
00 -
00 -
1.
4.
80.
0.
10.
180.
10.
13.
5.
70/yd
50/yd
3
00/ton
80/ft
00/ft
00/yd
00/yd
3
3
3
2
00/yrl2
00/yd
2
1.
3.
71.
17.
141.
162.
7.
9.
3.
30
30
50
70
20
50
10
50
60
2.
5.
- 88.
- 28.
- 353.
- 234.
- 11.
- 15.
6.
20/m
90/m
3
3
00/tonne
20/m
10/m
00/m
90/m
50/m
00/m
3
3
3
2
-continued-
-------
UNIT COSTS
USED AS BASIS FOR
COST ESTIMATES
(Continued)
oo
O
Item
No.
19.
20.
21.
22.
23.
24.
25.
26.
27.
Item
Bituminous concrete pavement**
4-cm (1.5- in.) depth
Bituminous concrete pavement**
13-cm (5-in.) depth
Reinforcing steel**
Steel sheet piling PMA-22**
18 m (60 ft)
Piles HP 10 x 42**
Exploratory boreholes**
5-cm (2-in.) diameter
30-mil PVC membrane
French drains**
30 x 30 cm (12 x 12 in.)
15-cm (6-in. ) foundation U-drains**
0.6 - 2.5 m (2 - 8 ft)
Range in
Dollars/Unit
1.50 -
3.50 -
0.40 -
6.00 -
7.00 -
3.00 -
0.30 -
1.00 -
3.00 -
2.50/yd2
4.50/yd2
0.60/lb
9.00/ft2
12.00/ft
10.00/ft
0.60/ft2
2.00/lin ft
5.00/lin ft
1.80 -
4.20 -
0.90 -
64.60 -
23.00 -
9.80 -
3.25 -
3.30 -
9.80 -
3.00/m2
5.40/m2
1.30/kg
96.90/m2
39.40/m
32.80/m
6.50/m2
6.60/m
16.40/m
-continued-
-------
UNIT COSTS
USED AS BASIS FOR
COST ESTIMATES
(Continued)
CO
Item
No.
Item
Range in
Dollars/Unit
28. 15-cm (6-in.) foundation U-drains**
2.5 - 5 m (8 - 16 ft)
29. Seeding and soil supplements**
30. Mulching, hay or straw**
31. Well point, installed**
32. Suction header, installed**
33. Suction pump, installed**
34. Deep well, 15-cm (6-in.) PVC,
drilled and installed**
35. Well screen, 30-m (10-ft) PVC
36. 1.3- to 2.7-kw (1- to 2-hp)
submersible pump and wiring
37. PVC connection piping
38. Chemical (sodium hypochlorite,
14 percent)
4.00 - 9.00/lin ft 13.10 - 29.50/m
0.10 - 0.15/yd2 1.20 - 1.80/m2
0.05 - 0.10/yd2 0.60 - 1.20/m2
10.00 - 15.00/unit
2.00 - 4.00/ft 6.60 - 13.10/m
2,000 - 3,000/unit
15.00/ft 49.20*/m
100.00/ea
800.00 - 1,000/ea
2.00 - 4.00/ft 6.60 - 13.10/m
0.42/gal
0.11/liter
-------
UNIT COSTS
USED AS BASIS FOR
COST ESTIMATES
(Continued)
Item
No.
39.
40.
41.
42.
CD
43.
44.
45.
46.
47.
Item
Labor for maintenance
Contract maintenance - drains (cleaning)
Contract maintenance - spray irrigation
Contract maintenance - at-grade irriga-
tion (ridge and furrow)
Contract maintenance - deep wells
Contract maintenance - well points
Portland cement or lime (FOB at plant)
Shipping cement or lime (100 miles)
Application of cement or lime for
Range in
Dollars/Unit
7.75/hour
1,080/year
500/year
185/year
386/year
1,080/year
30.00 - 31.
15.00 - 22.
50/ton
00/ton
13-cm (5-in) seal 1.85 - 2.10/yd2
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/2-78-142
3. RECIPIENT'S ACCESSION NO.
TITLE AND SUBTITLE
Guidance Manual
Disposal Sites
for Minimizing Pollution from Waste
5. REPORT DATE
August 1973 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
Andrew L. Tolman, Antonio P. Ballestero, Jr.,
William W. Beck, Jr., and Grover H. Emrich
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
A.W. Martin Associates, Inc.
900 W. Valley Forge Road
King of Prussia, Pennsylvania
10. PROGRAM ELEMENT NO.
1DC618 (SOS 3, Task 03)
19406
11. CONTRACT/GRANT NO.
68-03-2519
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final _
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer - Donald E. Sanning - 513/684-7871
16. ABSTRACT
This manual provides guidance in the selection of available engineering technology
to reduce or eliminate leachate generation at existing dumps and landfills. The
manual emphasizes remedial measures for use during or after closure of landfills
and dumps which do not meet current environmental standards. Most of the techniques
discussed in the report deal with the reduction or elimination of infiltration into
landfills in one of five categories, active groundwater or plume management, chemical
immobilization of wastes, and excavation and reburial. The technology presented is
widely used in construction but has not necessarily as yet been applied to landfill
closure. The report was submitted in fulfillment of Contract No. 68-03-2519 by
A.W. Martin Associates, Inc. of King of Prussia, Pennsylvania. The work was
completed May 17, 1978.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Attenuation, Barriers, Linings,
Deactivation, Stabilization, Bentonite,
Optimization, Waste Disposal, Sites,
Engineering Costs, Design Criteria
Groundwater Pollution
Leachate
Minimization
13B
68C
89B
18. DISTRIBUTION STATEMENT
PUBLIC DISTRIBUTION
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
93
20. SECURITY CLASS {This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
83-
&U.S. GOVERNMENT PRINTWG OFFICE 1978— "37 - MO/1425
------- |