SANITARY LANDFILL DESIGN AND OPERATION
U.S. ENVIRONMENTAL PROTECTION AGENCY
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EDITED MANUSCRIPT COPY
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SANITARY LANDFILL DESIGN AND OPERATION
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fll This report (SW-65ts) was written by
DIRK R. BRUNNER and DANIEL J. KELLER
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ENVIRONMENTAL PROTECTION AGENCY
| Region V, Library
230 South D--i.;,-: T^ctf
H Chicagog inj.;;n{:s Cc^;;^
U.S. ENVIRONMENTAL PROTECTION AGENCY
1971
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PROTOTOT AGETO
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FOREWORD
Sanitary Landfill Design and Operation is a state-of-the-art
treatise. It not only describes the known in sanitary landfill
technology, it also indicates areas in which research is needed.
H This publication represents the combined efforts of many
^_ individuals within the Federal solid waste management program,
~ other Federal agencies, State and local governments, private
H industry, and universities.
It is the hope of the Environmental Protection Agency that
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planners, designers, operators, and government officials will
use this document as a tool to help overcome the poor land
disposal practices that are evident today.
H. Lanier Hickman, Jr.
Deputy Director
Office of Solid Waste Management Programs
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CONTENTS
Chapter
H I THE SOLID WASTE PROBLEM 1
II SOLID WASTE DECOMPOSITION 5
B Leachate 6
tm Contaminant Removal 11
Decomposition Gas 14
I III HYDROLOGY AND CLIMATOLOGY 20
Surface Water 21
Groundwater 23
M Climatology 24
IV SOILS AND GEOLOGY 26
Soil Cover 28
Land Forms 38
V SANITARY LANDFILL DESIGN 41
M Volume Requirements 4]
Site Improvements 46
Clearing and grubbing 46
Roads /l£
__ Scales 47
Buildings j.q
I Utilities ^L
Fencing KQ
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Control of Surface Water
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Chapter
Groundwater Protection 53
Gas Movement Control 55
Permeable methods c-i
Impermeable methods cq
Landfilling Methods /,
Cell construction and cover material .......... /-i
Trench method .....................
Area method ...................... £,
Combination methods .................. s-,
Intermediate cover
Final cover
Maintenance 89
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Summary of Design Considerations 7>
SANITARY LANDFILL OPERATION ^
Hours of Operation jc Jg
Weighing the Solid Waste ?£ ^m
Traffic Flow and Unloading -1-1
Handling of Wastes 78 ^1
Residential, commercial, and industrial plant
wastes 79
Bulky wastes 8l
Institutional wastes 81
Dead animals 82
Industrial process wastes 82 I
Volatile and flammable wastes 84
Water and wastewater treatment plant sludges 34
Incinerator fly ash and residue gt;
Pesticide containers 85 *
Animal manure 85
Explosives and radioactive wastes 86 H
Placement of Cover Material 86
Daily cover 87 H
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mm Chapter
Weather Conditions
H Fires
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Salvage and Scavenging
VII EQUIPMENT
Equipment Functions
mm
Waste handl ing
Cover material handling ................ q7
Supportive functions .................. qo
Equipment Types and Characteristics
Landfill compactors
Scrapers
99
Crawler machines qq
Rubber-tired machines i«i
Size of Operation
Dragline ,,Q
- Special purpose equipment ,,«
Accessories i,.
Comparison of characteristics ,,r
Single-machine sites , i-,
Small sites ^o
Multiple-machine operation ,,q
mm Costs * . . ,19
mm Capital cost ^20
Operating and maintenance costs 120
VIM COMPLETED SANITARY LANDFILL 123
mm Characteristics J23
Decomposition ^23
Density j2li
Settlement ioli
Bearing capacity 126
Landfill gases ^27
Corrosion 127
VI I
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Chapter
Uses 127
Green area ^28
Agriculture J29
Construction
Municipal operations
Special districts
County operations
Private operations
Administrative Functions
BIBLIOGRAPHY
ACKNOWLEDGMENTS
Recreation j y>
Registration jno
IX MANAGEMENT 135
Administrative Agency ITC
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Finance joy
Operational cost control j on ^1
Performance evaluation i TO Bi
Personnel J/^Q
Public relations
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CHAPTER I
THE SOLID WASTE PROBLEM
B The Nation is emerging from a prolonged period in which it neglected
_ solid waste management, and it is becoming increasingly aware that our
present solid waste storage, collection, and disposal practices are in-
H adequate. Much of this awareness has been brought about by active cam-
paigns directed against air and water pollution and has resulted in a
11 third campaign--the abatement of land pollution.
_ The magnitude of the problem can be appreciated when we consider
that the Nation produced 250 million tons of residential, commercial,
H and institutional solid wastes in 1969. Only 190 million tons were col-
lected. Much of the remainder found its way to scattered heaps across
H the countryside, was left to accumulate in backyards and vacant lots,
_ or was strewn along our roadways. To compound the problem, an estimated
" 110 million tons of industrial wastes and nearly k billion tons of min-
H eral and agricultural wastes were generated.
Because of our affluence and increasing population, these quantities
I are expected to increase. In 1920, solid waste collected in our urban
_ areas amounted to only 2.75 lb per capita. In 1970, the figure stood
at over 5 Ib, and it is estimated that it will reach 8 Ib by 1980.
H Solid waste processing and disposal practices are grossly inadequate
for today's needs. Only 6 percent of land disposal operations and 25
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percent of incinerator facilities were considered adequate in the 1968
National Solid Wastes Survey.1
An acceptable alternative to the present poor practices of land
disposal is the sanitary landfill. This alternative involves the planning
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This inadequacy is the result of lack of planning and financing
and, until recently, public apathy with regard to our environment. There
has been far too little effort made to locate and reserve suitable areas
for land disposal operations in anticipation of community growth. Conse- H
quently, it is becoming more and more difficult to locate disposal sites
in urban areas. This directly affects disposal costs because hauling WM
expenses to a suitable landfill site increase or a more expensive alter-
native method of processing is required prior to disposal.
More than 90 percent of our Nation's solid waste is directly disposed H
of on land, the vast majority of it in an unsatisfactory manner. Open
and burning dumps, which are all too common, contribute to water and H
air pollution and provide food, harborage, and breeding grounds for mm
insects, birds, rodents, and other carriers of disease. In addition,
these dumps are unsightly and very often lessen the value of nearby land
and residences. In response to an aroused public, legislation has been
passed on the local, State, and federal levels to aid the development
of satisfactory disposal practices and to plan for all aspects of solid mm
waste management. The development and implementation of such plans will,
however, require the combined support of all citizens, industry, and H
government.
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|H and applying of sound engineering principles and construction techniques.
Sanitary landftiling is an engineered method of disposing of solid wastes
on land by spreading them in thin layers, compacting them to the smallest
practical volume, and covering them with soil each working day in a
manner that protects the environment. By definition, no burning of solid
waste occurs at a sanitary landfill. A sanitary landfill is not only
an acceptable and economic method of solid waste disposal, it is also
H an excellent way to make otherwise unsuitable or marginal land valuable.
Thorough planning and the application of sound engineering prin-
ciples to all stages of site selection, design, operation, and completed
use will result in a successful and efficient sanitary landfill. In
order to meet this objective, it is also essential to have an understanding
H of solid waste decomposition processeshow the many variables may affect
the decomposition rate, decomposition products, and how these factors
i may influence the environment. In essence, these relationships determine
j the physical stability of the fill and its potential to produce such
environmental problems as uncontrolled gas generation and movement and
H water pollution. Although these relationships are not fully understood,
sufficient knowledge is available to enable us to recognize potential
Bi problems and to plan and design sanitary landfills that will not harm
| the environment.
The final selection of a sanitary landfill site, its design, and
its operation should be based on a systematic, integrated study and an
evaluation of all physical conditions, economics, and social political
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restraints.
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REFERENCE
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Black, R. J., A. J. Muhich, A. J. Klee, H. L. Hickman, Jr., and _
R. D. Vaughan. The national solid wastes survey; an interim
report. [Cincinnati], U.S. Department of Health, Education, ^^
and Welfare, [1968]. 53 p.
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CHAPTER I I
SOLID WASTE DECOMPOSITION
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A knowledge of solid waste decomposition processes and the many
H influences they exert is essential to proper san'tary landfill site
selection and design.
I Solid wastes deposited in a landfill degrade chemically and bio-
logically to produce solid, liquid, and gaseous products. Ferrous and
other metals are oxidized; organic and inorganic wastes are utilized
H by microorganisms through aerobic and anaerobic synthesis. Liquid waste
products of microbial degradation, such as organic acids, increase
H chemical activity within the fill. Food wastes degrade quite readily,
M while other materials, such as plastics, rubber, glass and some demo-
lition wastes, are highly resistant to decomposition. Some factors that
affect degradation are the heterogeneous character of the wastes, their
physical, chemical, and biological properties, the availability of oxygen
H and moisture within the fill, temperature, microbial populations, and
type of synthesis. Since the solid wastes usually form a very heterogeneous
mass of nonuniform size and variable composition and other factors are
complex, variable, and difficult to control, it is not possible to accu-
rately predict contaminant quantities and production rates.
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Biological activity within a landfill generally follows a set pat-
tern. Solid waste initially decomposes aerobically, but as the oxygen
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supply is exhausted, facultative and anaerobic microorganisms predomi- II
nate and produce methane gas, which is odorless and colorless. Tempera-
tures rise to the high mesophi1ic-low thermophilic range (60 to 150 F) |
because of microbial activity. Characteristic products of aerobic de- _
composition of waste are carbon dioxide, water, and nitrate. Typical
products of anaerobic decomposition of waste are methane, carbon dioxide, H
water, organic acids, nitrogen, ammonia, and sulfides of iron, manganese
and hydrogen.
Leachate
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Groundwater or infiltrating surface water moving through solid waste H
can produce leachate, a solution containing dissolved and finely suspended
solid matter and microbial waste products. Leachate may leave the fill J|
at the ground surface as a spring or percolate through the soil and rock _
that underlie and surround the waste. ^
Composition of leachate is important in determining its potential II
effects on the quality of nearby surface water and groundwater. Con-
taminants carried in leachate are dependent on solid waste composition H
and on the simultaneously occurring physical, chemical, and biological _
activities within the fill. Identification of leachate composition has ^
been the object of several laboratory lysimeter and field studies.1"6 II
The chemical and biological characteristics of leachate were de-
termined in two studies conducted over a period of time with solid waste ^
of the same general type at both sites (Table 1). The data exhibit a
significant range of values. As an example, pH of the leachate investigated
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Component
pH
Hardness, CaCO
Alkalinity, CaCO
Ca
Mg
Na
K
Fe (total)
Ferrous i ron
Chloride
Sulfate
Phosphate
Organ! c-N
NH^-N
BOD
COD
Zn
Ni
Suspended sol ids
^Average compos
per cubic foot of a
+0ne determinat
COMPOSITION
FROM MUN
Low
6
890
730
240
64
85
28
6
8
96
84
0
2
0
21,700
TABLE 1
OF INITIAL LEACHATE*
1C 1 PAL SOLID WASTE
Study A1
High
.0 6.5
7,600
9,500
2,330
410
1,700
1,700
.5 220
.7f 8.7+
2,350
730
.3 29
.4 465
.22 480
30,300
ition, mg per liter of first 1.3 1
compacted ,
ion.
representative, munici
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Study B2
Low High
3-7 8.5
200 550
127 3,800
0.12 1,640
47 2,3kO
20 375
2.0 130
8.0 482
2.1 177
809 50,715
0.03 129
0.15 0.81
13 26,500
iters of leachate
pal sol id waste.
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in study A was found to vary between 6.0 and 6.51 while pH in study B
varied between 3-7 and 8.5-2 Chloride varied from 96 to 2,350 mg per
liter in study A and from k~l to 2,3^0 in study B. Although the leachates
for the two studies were similar in many respects, there were differences
which further indicate the variability of leachate composition with time
for individual sites and between sites. For example, mean sulfate con-
centrations were 61 ^ mg per liter for study A, ranging from 730 near
the start of the test to 8k near the conclusion. Sulfate concentrations
in study B averaged 152 mg per liter, ranging from 375 at the beginning
of sampling to 20 at the conclusion.
The quantity of contaminants in leachate from a completed fill where H
no more waste is being disposed of can be expected to decrease with time.
Only a few studies have attempted to determine the effect of long term §
leaching of solid waste.1'3 Much more research is needed in the laboratory M
and in the field to adequately describe this phenomena. The limited
data available indicate a removal of large quantities of contaminants
by leaching during active stages of decomposition, and a slackening off
of removal as the fill stabilizes (Figures 1,2). If the fill is con-
sidered as a mass of material containing a finite amount of leachabie mm
material, then depending on the removal rate, leaching should eventually
cease.
The types and quantities of contaminants that enter the receiving
water and the ability of that water to assimilate these contaminants
will determine the degree of leachate control needed. In some cases mm
it may be established that introduction of leachate will not upset the
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ecology or usefulness of the receiving water. Careful examination of
dilution and oxygen demand criteria of the stream can be useful tools
in showing the ability of a stream to assimilate leachate. In all cases,
water quality criteria and the laws and ordinances of federal, State,
H and local agencies pertaining to water pollution must be followed.
Some investigators believe that even in a sanitary landfill, leachate
I production is inevitable and that some leachate will eventually enter
surface water or groundwater. This has not been proven but neither has
the opposite view. The present philisophy held by the Solid Waste Manage-
H ment Office, most State solid waste control agencies, and many experts
in the field is that through sound engineering and design, leachate pro-
duction and movement may be prevented or minimized to the extent that
it will not create a water pollution problem. The most obvious means
of controlling leachate production and movement is to prevent water from
H entering the fill to the greatest extent practicable.
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Contaminant Removal
Leachate percolating through soils underlying and surrounding the
solid waste is subject to purification (attenuation) of the contaminants
H by ion exchange, filtration, adsorption, complexing, precipitation, and
biodegradation. It moves either as an unsaturated flow if the voids
^^ in soil are only partially filled with water or as a saturated flow if
they are completely filled. The type of flow affects the mechanism of
attentuation, as do soil particle size and shape and soil composition.
H Attentuation of contaminants flowing in the unsaturated zone is
generally greater than in the saturated zone because there is a greater
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potential for aerobic degradation, adsorption, complexing, and ion exchange
of organics, inorganics, and microbes. Aerobic degradation of organic
matter is more rapid and complete than anaerobic degradation. Because H
the supply of oxygen is extremely limited in saturated flow, anaerobic
degradation prevails. Adsorption and ion exchange are highly dependent |
on the surface area of the liquid and solid interface. The surface area M
to flow volume ratio is greater in an unsaturated flow than in a saturated
flow.
Leachate travel in the saturated zone is primarily controlled by
soil permeability and hydraulic gradient, but a limited amount of capillary J|
diffusion and dispersion do occur. The leachate is diluted very little _
in groundwater unless a natural geologic mixing basin exists. Leachate
movement will closely follow the streamlines of groundwater flow.
Information on leachate travel in the unsaturated zone is lacking.
Most of the studies made of domestic and industrial wastewaters traveling B
through the unsaturated zone indicate that the organic and microbial mm
removal level achieved is very good. As an example, when a citrus liquid
waste was applied to the ground surface, COD was reduced from 5,000 mg H
per liter to less than 100 in the top 3 ft of soil,7 However, the rate
and frequency at which the waste liquid is applied, and the type of soil B
have great influence on attenuation efficiency. Nitrification can also
occur in the unsaturated soil zone and produce nitrate and nitrite from
ammonia-nitrogen. A water that was bacteriologically safe, according H
to USPHS Drinking Water Standards for the coliform group, was obtained
by percolating settled domestic waste water through at least A ft of |
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a fine, sandy loam soil.8 This last study is especially important since
BB pathogens have been detected in solid waste and leachate.^' 1°
| Travel of leachate in the saturated zone has been monitored by sev-
eral investigators ,4)5»-11 but more research is needed to clearly define
its significance. Results obtained so far indicate that the distance
the contaminants travel depends on the composition of the soil, its
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permeability, and the type of contaminant. Organic materials that are
j biodegradable do not travel far, but inorganic ions and refractive
organics can travel appreciable distances. Some inorganic contaminants
from a dump located in an abandoned gravel pit have been traced for 1,200
ft.4 Contaminant movement was through a highly porous glacial alluvium.
i Another study indicates that the rate of movement through some soils
is so slow, that the full impact of contaminant travel may not be realized
for many years.5 If contaminant travel is slow, the release of contami-
H nants to an aquifer would also be slow.
Inorganic materials appear to be most resistant to attenuation.
This is especially true of chloride ion, and it serves, therefore, as
a good indicator of leachate movement. Data from monitoring wells sur-
rounding a landfill in Illinois reflected a sharp increase in chlorides
and total dissolved solids (Table 2). Chloride concentrations in the
unaffected groundwater were 18 mg per liter, those in the fill were 1,710,
i and those in a monitoring well 150 ft downstream of the fill were 248.
Natural purification processes have only a limited ability to remove
contaminants, because the number of adsorption sites and exchangeable
H ions available is finite. In addition, the processes are time dependent--
residence time is shortened by high flow rates. Flow rates through soils
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near landfills may be reduced naturally by filtering and settling of «
suspended contaminants. Porosity and permeability of the soil are then
reduced. Thus additional protection against contaminant travel may be H
possible as time passes. (Analysis of precipitation, flooding, upland
drainage, and evapo-transpiration necessary to determine whether leaching ||
will occur at a site is discussed later.)
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TABLE 2
GROUNDWATER QUALITY IN THE VICINITY OF A LANDFILL5 I
Characteristi c
Total dissolved solids
PH
COD
Total hardness
Sod i urn
Chlori de
Background
mg/1
636
7.2
20
570
30
18
Fill*
mg/1
6,712
6.7
1,863
4,960
806
1,710
Moni tor wel 1*
mg/1
1,506
7.3
71
820
316
2i>8
*Groundwater quality in a saturated fill and in a monitoring well
located approximately 150 ft downstream from the landfill at a depth of
11 ft in sandy, clayey silt.
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Decomposition Gas ^^
Gas is produced naturally when solid wastes decompose. The quantity
generated in a landfill and its composition depend on the types of solid
waste that are decomposing. A waste with a large fraction of easily
degradable organic material will produce more gas than one that consists
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largely of ash and construction debris. The rate of gas production is
i governed solely by the level at which microbial decomposition is occurring
j in the solid waste. When decomposition ceases, gas production also ends.
In a field study conducted over a 907~day period, approximately 40 cu
H ft of gas were produced per cu yd of solid waste.12 Gas production was
monitored throughout the duration of this study (Figure 3)- Theoretically,
if decomposition is carried to completion, each Ib of solid waste contain-
ing 25 percent inerts can produce up to 6.6 cu ft of gas.
Methane and carbon dioxide are the major constituents of landfill
H decomposition gas, but other gases are also present and some may impart
a repugnant odor. Hydrogen sulfide, for example, may be generated at
a landfill, especially if it contains a large amount of sulfate, such
j as gypsum board (calcium sulfate) or if brackish water infiltrates the
solid waste.
H Limited studies have been made on the varying composition of landfill
gas over a period of time (Table 3). The data indicate that the percentage
of carbon dioxide and methane present three months after solid wastes
were placed in the fill was 88 and 5, respectively; four years later
the respective figures were 51 and 48. Very little methane is produced
H during early stages of decomposition because aerobic synthesis prevails.
Landfill gas is important to consider when evaluating the effect
i a landfill may have on the environment because methane can explode and
j because mineralization of groundwater can occur if carbon dioxide dissolves
and forms carbonic acid. Methane is explosive only when present in air
at concentrations between 5 and 15 percent. Since there is no oxygen
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present in a landfill when methane concentrations in it reach this critica
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level, there is no danger of the fil
vents into the atmosphere (its spec!
air) it may accumulate in buildings
to a sanitary landf i 1 1 .
1 exploding. If, however, methane
fie gravity is less than that of
or other enclosed spaces on or close
TABLE 3
LANDF I-LL GAS
Time interval since start
of cell completion
(months)
0-3
3-6
6-12
12-18
18-24
24-30
30-36
36-42
42-48
The potential movement of gas i
to consider when selecting a site.
COMPOSITION12
Average percent by volume
2 2 4
5.2 88 5
3.8 76 21
0.4 65 29
1.1 52 40
. 0.4 53 47
0.2 52 48
1.3 46 51
0.9 50 47
0.4 51 48
s, therefore, an essential element
It is particularly important if en-
closed buildings are built on or adjacent to the sanitary landfill or
if it is to be located near existing
dent i a) areas.
industrial, commercial, and resi-
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Gas permeability of the soils surrounding the landfill can influence ^^
the movement of decomposition gas. A dry soil will not significantly ^*
impair its flow, but a saturated soil, such as clay, can be an excellent H
barrier. A well-drained soil acts as a vent to gas flow. If cover
material acts as a barrier, then the landfill gases will migrate laterally
until they can vent to the atmosphere. More research is needed to re- ^
liably predict rate and distance of gas movement.
Landfill gas movement can be controlled if sound engineering prin- !
ciples are applied. Of the several methods that have been devised and
tested, permeable vents and impermeable barriers are the two basic types.
Both are discussed in Chapter V.
REFERENCES
*Note: This land disposal site does not meet the standard for a
sanitary landfill.
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1. California State Water Pollution Control Board. Report on the
investigation of leaching of a sanitary landfill. Publication
No. 10. Sacramento, 195^*. [92 p.]
2. Fungaroli, A. A. Pollution of subsurface water by sanitary land-
fill. (In preparation.) tji
3. Qasim, S. R. Chemical characteristics of seepage water from simu-
lated landfills. Ph.D. Dissertation, West Virginia University, M
Morgantown, 1965- 1^*5 p.
k. Andersen, J. R., and J. N. Dornbush. Influence of sanitary landfill
on ground water quality. Journal American Water Works Association,
59(4):457-470, Apr. 1967.*
5. Hughes, G. M., R. A. Landon, R. N. Farvolden. Hydrogeology of solid ft|
waste disposal sites in northeastern Illinois; an interim report on ||
a solid waste demonstration grant project. [Cincinnati], U.S.
Department of Health, Education, and Welfare, 19&9- 137 p.
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6. Ministry of Housing and Local Government. Pollution of water by
tipped refuse; report of the Technical Committee on the experi-
mental disposal of house refuse in wet and dry pits. London,
Her Majesty's Stationery Office, 1961. 141 p.
7. Anderson, D. R., W. D. Bishop, and H. F. Ludwig. Percolation of
citrus wastes through soil. In Proceedings; 21st Industrial
Waste Conference, May 3~5, 19&F- LaFayette, Ind., Purdue Uni-
versity, p. 892-901.
8. California State Water Pollution Control Board. Field investiga-
tion of waste water reclamation in relation to ground water
pollution. Publication No. 6. Sacramento, 1953. 124 p.
9. Weaver, L. Refuse disposal, its significance. JJT_ Ground Water
Contamination; Proceedings of the 1961 Symposium, Cincinnati,
Apr. 5-7, 1961. Technical Report W61-5. Robert A. Taft Sanitary
Engineering Center, p. 104-110.
10. Cook, H. A., D. L. Cromwell, and H. A. Wilson. Microorganisms
in household refuse and seepage water from sanitary landfills.
In Proceedings; West Virginia Academy of Science, 39:107-114.
1967.
11. County of Los Angeles, Department of County Engineer and Engineering-
Science, Inc. Development of construction and use criteria for
sanitary landfills; an interim report. Cincinnati, U.S. Department
of Health, Education, and Welfare, 1969- [267 p.]
12. Merz, R. C., and R. Stone. Special studies of a sanitary landfill.
Washington, U.S. Department of Health, Education, and Welfare,
1970. (Distributed by National Technical Information Service,
Springfield, Ma., as PB-196 148. 240 p.)
19
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CHAPTER I I I
HYDROLOGY AND CLIMATOLOGY
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A major consideration in selecting the site for a sanitary landfill
and in designing it is the hydrology of the area. To a large extent,
hydrology will determine whether the formation of leachate will produce ^^
a water pollution problem. ^B
When solid wastes are placed in a sanitary landfill, they may vary
tremendously with regard to moisture content. Wood, concrete, and other
construction rubble may have very little, whereas many food wastes may H
be extremely wet. Paper, a major constituent of solid waste, is usually
quite low in moisture. Metals and glass are also generally present in
solid waste but are essentially free of moisture.
In general, the moisture content of mixed solid waste generated
by a community ranges from 20 to 30 percent by weight. (Wide fluctuations
can occur depending on climatic conditions during storage and collection.)
In this general range, the moisture alone should not produce leachate H
provided the solid waste is fairly well mixed and has been well compacted. [
The water that results from decomposition of the relatively small amounts
of intermixed food wastes and other moist, readily degradable organics
can be absorbed by the relatively large amounts of paper and other dry
components present. H
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Leachate is not produced until all of the sanitary landfill or a
Hj sizable portion of it becomes saturated by water entering it from out-
side. For this reason, it is extremely important that a study of the
fj§ site hydrology be made. Precipitation, surface runoff characteristics,
^m evapo-transpiration, and the location and movement of groundwater with
relation to the solid waste are the major factors that should be considered,
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Surface Water
Surface water that infiltrates the cover soil and enters the under-
lying solid waste can increase the rate of waste decomposition and
eventually cause leachate to leave the solid waste and create water pol-
H lution problems. Unless rapid decomposition is planned and the sanitary
landfill is so designed that leachate is collected and treated, as much
JJ surface water as is practicable should be kept from entering the fill.
The permeability of a soil is the measure of the ease or difficulty
with which water can pass through it. This is greatly affected by the
texture, gradation, and structure of the soil and the degree to which
it has been compacted. Coarse grained soils (gravels and sands) are
usually much more permeable than fine grained soils (silts and clays).
^_ However, small amounts of silts and clays (fines) in a coarse grained
soil may greatly decrease permeability while cracks in fine grained soils
II may do the opposite."
The quantity of water that can infiltrate the soil cover of a sani-
J| tary landfill depends not only on these physical characteristics but
"Specific information on the percentage of water infiltrating a
particular soil can be obtained from the Soil Conservation Service, U.S.
Department of Agriculture.
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also on the residence time of the surface water. It can be minimized
by: (1) diverting upland drainage; (2) grading and sloping the daily
and final cover to allow for runoff; (3) decreasing the permeability
of the cover material.
There have been few detailed investigations made of the quantity
of moisture that can enter a sanitary landfill through a cover and on
the amount and quality of water that may leave the fill and enter an mm
aquifer or stream. One investigator claims, however, that it is possible WM
to predict the quantity of surface water that will enter the underlying
solid waste if the available water storage capacity, quantity, and fre-
quency of water infiltration, and rates of evaporation and transpiration
for a cover material are known.1 Under ideally controlled laboratory
conditions or at a field test site, this would seem plausible, but more
studies must be made of leaching potentials at operational sanitary land-
fills. These are needed because the placement of cover soils cannot
be rigidly controlled and some discontinuities always develop in the
structure of a sanitary landfill. They derive from variations in soil H
thickness, texture, and degree of compaction as well as from slight mm
changes that occur in the grade or slope of the cover soil when it
settles; this may cause cracks or fissures to develop. Furthermore, H
slight variations in the amount or intensity of rainfall, minor changes
in vegetation, or other presumably less important alterations of the H
fill's final surface may have major effects on the amount of surface mm
moisture entering the solid waste.
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Groundwater
Groundwater is water that is contained within the zone of saturation
of soil or rock that is, all the pores in the containing earth materials
are saturated. This zone is just beneath the land surface in many parts
B of the country and is on the surface at many springs, lakes, and marshes.
H In some areas, notably most of the arid west, the zone of saturation
is deep in the ground.
H The water table is the surface where water stands in wells at atmos-
pheric pressure. In highly permeable formations, such as gravel, the
| water table is essentially the top of the zone of saturation. In many
M fine grained formations, however, capillary action causes water to rise
above this zone and the inexperienced observer might think this capillary
fringe is part of the zone.
The zone of saturation commonly is not continuous with depth nor
I does it necessarily have lateral continuity. In exploring for underground
_ water, a saturated zone may be found that yields water at a shallow depth,
but if the exploration hole is continued, dry material is encountered
H at a greater depth and then another zone of saturation is found. Isolated
high zones or lenses of saturated material are referred to as perched
|| water. Perched water is common to glacial soil (till plain) areas where
interstrat i f ied lenses or patches of porous sand and gravel are underlaid
by relatively impervious glacial clay.
H Because the conditions affecting groundwater occurrence are so com-
plex, it is essential that the sanitary landfill site investigation include
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an evaluation by a qualified groundwater hydrologist. This is needed _
not only to locate the zone of saturation but also to predict the
direction and rate of flow of groundwater and the quality of the aquifer. H
Leachate from a landfill can contaminate groundwater. In order
to determine if leachate will produce a subsurface pollution problem,
It is essential that the quality of the groundwater be established and _
that the aquifer's flow rate and direction be determined. Water within
the zone of saturation is not static. It moves vertically and laterally Hj
at varying rates, depending on the permeability of the soil or rock
formation in which it is located and the external hydraulic forces acting ||
upon i t . _
The movement of groundwater is determined by using a tracer such ^
as fluorescein dye or by making piezometer readings. The estimated quan- H
tity of groundwater flow is based on the permeability of the aquifer,
effective cross -sectional flow area, and the pressure gradient that induces H
the water to move. The groundwater hydrologist should also determine ^_
whether the aquifer is in a discharge or recharge area. In a discharge
area, water leaves the aquifer and emerges through the ground surface
as a spring. In recharge areas, water infiltrates the ground and enters
the aquifer. Lakes, streams, and rivers may serve as recharge or discharge fj
areas, or both, depending on the surrounding groundwater level and geologic
conditions.
C^l imatology
Wind, rain, and temperature directly affect sanitary landfill design
and operation. Windy sites need to have litter fences at the operating
2k
_
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_ area and personnel to clean up the area at the end of the day. Such
^^ sites can also be very dusty when the soil dries, and this may irritate
Bj people living or working nearby. Trees planted on the perimeter of a
sanitary landfill help keep dust and litter within the site. Water
K sprinkling or the use of other dust palliatives are often necessary along
^m haul roads constructed of soil, crushed stone, or gravel.
^ The effect of rain that infiltrates the sanitary landfill and in-
II fluences solid waste decomposition has been discussed previously. Rain
can also cause operational problems; many wet soils are difficult to
I spread and compact, and traffic over such soils is impeded.
_ Freezing temperatures may also cause problems. If the frost line
is more than 6 in. below the ground surface, cover material may be diffi-
j cult to obtain. A crawler dozer equipped with a ripper may be required,
or it may be necessary to stockpile cover soil and protect it from
ff freezing. A well-drained soil is more easily worked in freezing weather
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than one that is poorly drained.
REFERENCE
1. Remson, I., A. A. Fungarol i , and A. W. Lawrence. Water movement
in an unsaturated sanitary landfill. Journal of the Sanitary
Engineering Division, Proc. ASCE, 9MSA2) : 307-31 7 , Apr. 1968.
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CHAPTER IV
SOILS AND GEOLOGY
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A study of the soils and geologic conditions of any area in which
a sanitary landfill may be located is essential to understanding how II
its construction might affect the environment. The study should outline
the limitations that soils and geologic conditions impose on safe, effi- |
cient design and operation. _
A comprehensive study identifies and describes the soils present,
their variation, and their distribution. It describes the physical and H
chemical properties of bedrock, particularly as it may relate to the
movement of water and gas (Figure k). Permeability and workability are H
essential elements of the soil evaluation, as are stratigraphy and struc-
ture of the bedrock.
Rock materials are generally classified as sedimentary, igneous, |H
or metamorphic. Sedimentary rocks are formed from the products of erosion
of older rocks and from the deposits of organic matter and chemical pre- gj
cipitates. Igneous rocks derive from the molten mass in the depths of ^_
the earth. Metamorphic rocks are derived from both igneous and sedi- ^^
mentary rocks that have been altered chemically or physically by intense H
heat or pressure.
Sands, gravels, and clays are sedimentary in origin. The sedl- |
mentary rocks, sometimes called aqueous rocks, are often very permeable
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PH
PH S
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and therefore represent a great potential for the flow of groundwater.
I
Should leachate occur and enter the rock strata, contaminant travel would
usually be greatest in sedimentary formations. Other rocks commonly ^1
classed as sedimentary are limestone, sandstone, and conglomerates.
Fracturing and jointing of sedimentary formations are common, and they
increase permeability. In fact, the most productive water-bearing strata
for wells are formations of porous sandstone, highly fractured limestone,
and sand and gravel deposits. Siltstones and shales, which are also H
of sedimentary origin, usually have a very low permeability unless they
have been subjected to jointing and form a series of connected open ^"
fractures.
Igneous and metamorphic rocks, such as shist, gneiss, quartzite,
obsidian, marble, and granite, generally have a very low permeability. H
If these rocks are fractured and jointed, however, they can serve as
aquifers of limited productivity. Leachate movement througn them should
not, therefore, be categorically discounted. H
Information concerning the geology of a proposed site may be ob-
tained from the U.S. Geological Survey, the U.S. Army Corps of Engineers, H
State geological and soil agencies, university departments of soil ^
sciences and geology, and consulting soil engineers and geologists. ^
Soil Cover 91
The striking visual difference between a dump and a sanitary land- H
fill is the use of soil cover at the latter. Its compacted solid waste
_
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is fully enclosed within a compacted earth layer at the end of each op-
erating day, or more often if necessary.
H The cover material is intended to perform many functions at a sani-
tary landfill (Table k); ideally, the soil available at the site should
be capable of performing all of them.
| The cover material controls the ingress and egress of flies, dis-
courages the entrance of rodents seeking food, and prevents scavenging
birds from feeding on the waste. Tests have demonstrated that 6 in.
of compacted sandy loam will prevent fly emergence.1 Daily or more
frequent application of soil cover greatly reduces the attraction of
birds to the waste and also discourages rodents from burrowing to get
food. The cover material is essential for maintaining a proper appearance
H of the sanitary landfill.
Many soils, when suitably compacted, have a low permeability, will
not shrink, and can be used to control moisture that might otherwise
j enter the solid waste and produce leachate.
Control of gas movement is also an essential function of the cover
material. Depending on anticipated use of the completed landfill and
the surrounding land, landfill gases can be either blocked by or vented
through the cover material. A permeable soil that does not retain much
water can serve as a good gas vent. Clean sand, well-graded gravel,
or crushed stone are excellent when kept dry. If gases are to be prevented
from venting through the cover material, a gas-impermeable soil with
high moisture-holding capacity compacted at optimum conditions should
H be used.
29
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II Enclosing the solid waste within a compacted earth shell offers
some protection against the spread of fire. Almost all soils are non-
JH combustible, thus the earth side walls and floor help to confine a fire
_ within the cell. Top cover over a burning cell offers less protection
^^ because it becomes undermined and caves in, thus exposing the overhead
Hj cell to the fire. The use of a compactible soil of low permeability
is an excellent fire-control measure because it minimizes the flow of
g| oxygen into the fill.
_ To maintain a clean and sightly operation, blowing litter must be
^ controlled. Almost any workable soil satisfies this requirement, but
H fine sands and silts without sufficient binder and moisture content may
create a dust problem.
|| The soil cover often serves as a road bed for collection vehicles
^ moving to and from the operating area of the fill. When it is, it should
be trafficable under all weather conditions. In wet weather, most clay
soils are soft and slippery.
In general, soil used to cover the final lift should be capable
|| of growing vegetation. It should, therefore, contain adequate nutrients
_ and have a large moisture-storage capacity. A minimum compacted thickness
^^ of 2 ft is recommended.
H Comparison of the soil characteristics needed to fulfill all of
these functions indicates that some anomalies exist. To serve as a road
j base, the soil should be well-drained so that loaded collection vehicles
_ do not bog down. On the other hand, it should have a low permeability
if water is to be kept out of the fill, fire is to be kept from spreading,
31
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and gas is not to be vented through the final cover. These differences _
can be solved by placing a suitable road base on top of the normally ^
low permeability-type cover material. A reverse situation occurs when H
landfill gases are to be vented uniformly through the cover material.
The soil should then be gas permeable, have a small moisture-storage ||
capacity, and not be highly compacted. As before, the criteria for
moisture and fire control require the soil to have a low permeability.
Leachate collection and treatment facilities may be required if a II
highly permeable soil is used to vent gas uniformly through the cover
material; if this is not done, an alternative means of venting gas H
through the cover material must be sought.
There are many soils capable of fulfilling the functions of cover
material. Minor differences in soil grain size or clay mineralogy can B
make significant differences in the behavior of soils that fall within
a given soil group or division. In addition, different methods of ||
placing and compacting the same soil can result in a significantly dif- ^
ferent behavior. Moisture content during placement, for example, is
a critical factoiit influences the soil's density, strength, and porosity.
The soils present at proposed sites should be sampled by augering,
coring, or excavating, and then be classified. The volume of suitable ||
soil available for use as cover material can then be estimated and the «
depth of excavation for waste disposal can be determined. Specific infor-
mat ion on the top 5 ft of the soil mantle can often be obtained from
the Soil Conservation Service, U.S. Department of Agriculture.
Sanitary landfilling is a carefully engineered process of solid ||
waste disposal that involves appreciable excavating, hauling, spreading, _
32
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^_ and compacting of earth. When manipulating soils in this manner, the
^ Unified Soil Classification System (USCS) is useful. Although recommenda-
H tions for soil to be used at a landfill are often expressed in the U.S.
Department of Agriculture textural classification system (Figure 5),
|| the USCS is preferred because it relates in more detail the workability
« of soils from an engineering viewpoint (Table 5).
Clay soils are very fine in texture even though they commonly con-
H
tain small to moderate amounts of silt and sand. They vary greatly in
their physical properties, which depend not only on the small particle
| size but on the type of clay minerals and soil water content. When dry,
_ a clay soil can be almost as hard and tough as rock and can support heavy
loads. When wet, the same soil often becomes very soft, is sticky or
H slippery, and is very difficult to handle. A clay soil swells when it
becomes wet, and its permeability is very low.
11 Many clay soils can absorb large amounts of water but, after drying,
usually shrink and crack. These characteristics make many clays less
desirable than other soils for use as a cover material. The large cracks
I that usually develop allow water to enter the fill and permit decomposition
gases to escape. Rats and insects can also enter or leave the fill through
|f these apertures.
_ Clay soil can, however, be used for special purposes at a landfill.
If it is desirable to construct an impermeable lining or cover to control
IH leachate and gas movement, many clays can be densely compacted at optimum
moisture. Once they are in place, it is almost always necessary to keep
them moist so they do not crack.
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100
Sand 2.0 to 0.05 mm. diameter
Silt 0.05 to 0.002 mm. diameter
Claysmaller than 0.002 mm. diameter
90
10
...
xpft Si" loam JM
100 90 80 70 60 50 40 30 20 10
Per cent sand
COMPARISON OF PARTICLE SIZE SCALES
Sieve Openings in Inches U. S. Standard Sieve Numbers
32 I'/? 1 fo V/» 4 10 20 40 60 200
nTTTTTTT I I II I I I III I I I
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USDA
GRAVEL
SAND
Very
Coarse
uses
GRAVEL
Coa-se Fine
Coarse 1 Medium
"" IBS
SILT
CLAY
'
SAND
Coarse
Medium
Fine
SILT OR CLAK
JLL_J I I I I I
J_J I II I . . .
2 1 0.5/0.42 0.25 o7l\ 0.05 0.02 0.01 0.005 002 0.001
Grain Size in Millimeters 0.074
Fifure 5. Textural classification chart (U.S. Department of
Agriculture) snd comparison of particle size scales.
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The suitability of coarse-grained material (gravel and sand) for
cover material depends mostly on grain size distribution (gradation),
the shape of grains, and the amount of clay and silt fines present. If ^1
gravel, for example, is poorly graded and relatively free of fines, it
is not suitable as cover material for moisture, gas, or fly control.
It cannot be compacted enough, and the gravel layer will be porous and
highly permeable; this would allow water to enter the fill easily. Flies
would have little difficulty emerging through the loose particles. On H
the other hand, a gravel layer no more than 6 in. deep would probably ^^
discourage rats and other rodents from burrowing into the fill and would ^
provide good litter control. If gravel is fairly well-graded and contains
10 to 15 percent sand and 5 percent or more fines, it can make an excellent
cover. When compacted, the coarse particles maintain grain-to-grain
contact, because they are held in place by the binding action of the
sand and fines and cohesion of the clays. The presence of fines greatly Bi
decreases a soil's permeability. A well-graded, sandy, clayey gravel
does not develop shrinkage cracks. It can control flies and rodents,
provide odor control, can be worked in any weather, and supply excellent
traction for collection trucks and other vehicles. ^^
Many soils classified as sand (grain size generally in the range «
of 4.0 to 0.05 mm) contain small amounts of silt and clay and often some
gravel-size material as well. A well-graded sand that contains less
than 3 percent fines usually has good compaction characteristics. A H
small increase in fines, particularly silt, usually improves density
and allows even better compaction. A poorly graded sand is difficult §
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to compact unless it contains abundant fines. The permeability of clean
sand soils is always high, even when compacted, and they are not, therefore,
suitable for controlling the infiltration of water. They are also ineffective
in constraining flies and gases.
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A well-drained sandy soil can be easily worked even if temperatures
fall below freezing, while a soil with a large moisture-storage capacity
wi11 freeze.
H Practically the only soils that can be ruled out for use as cover
material are peat and highly organic soils. Peat is an earthy soil (usually
I brown to black) and is composed largely of partially decomposed plant
mm matter. It usually contains a high amount of voids, and its water content
may range from 100 to ^00 percent of the weight of dried solids. Peat
H is virtually impossible to compact, whether wet or dry. Peat deposits
are scattered throughout the country but are most abundant in the States
| bordering the Great Lakes. Highly organic soils -include sands, silts,
mm and clays that contain at least 20 percent organic matter. They are
usually very dark, have an earthy odor when freshly turned, and often
contain fragments of decomposing vegetable matter. They are very diffi-
cult to compact, are normally very sticky, and can vary extremely in
H their moisture content.
mm Many soils contain stones and boulders of varying sizes, especially
those in glaciated areas. The use of soils with boulders that hinder
H compaction should be avoided.
Soil surveys prepared by the Soil Conservation Service of the U.S.
| Department of Agriculture are available for a major portion of the
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country. Local assistance in using and interpreting them is available
through soil conservation districts located in some 3,000 county seats
throughout the United States. The surveys cover such specific factors H
as natural drainage, hazard of flooding, permeability, slope, workability,
depth to rock, and stoniness. They are commonly used to locate potential ^1
areas for sanitary landfills. They also can serve as the basis for de-
signing effective water management systems and selecting suitable plant
cover to control runoff and erosion during and after completion of fill H
operations. Sanitary landfill owners and their consultants can avoid
costly investigations of unsuitable sites by using soil surveys to select
areas for which detailed investigations appear warranted. Using soil H
surveys for the foregoing purposes does not, however, eliminate the need
for making detailed site investigations. H
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Land Forms
A sanitary landfill can be constructed on virtually any terrain,
but some land forms require that extensive site improvements be made
and expensive operational techniques followed. Flat or gently rolling H
land not subject to flooding is best, but this type is also highly desirable
for farming and industrial parks, and this drives up the purchase price. ^
Depressions, such as canyons and ravines, are more efficient than H
flat areas from a land use standpoint since they can hold more solid
waste per acre. Cover material may, however, have to be hauled in from H
surrounding areas. Depressions usually result when surface waters run
off and erode the soil and rock. By their nature, they require special |
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measures to keep surface waters from inundating the fill. Permeable
formations that intersect the side walls or floor of the fill may also
have to be lined with an impervious layer of clay or other material to
control the movement of fluids.
There are also numerous man-made topographic features scattered
over the country--strip mines, worked-out stone and clay quarries, open
pit mines, and sand and gravel pits. In most cases, these abandoned
depressions are useless, dangerous eyesores. Many of them could be
safely and economically reclaimed by utilizing them as sanitary landfills.
Clay pits, for example, are located in most impermeable formations, which
^^ are natural barriers to gas and water movement. Abandoned strip mines
also are naturally suited for use as sanitary landfills. Most coal
formations are underlaid by clays, shales, and siltstones that have a
very low permeability. When permeable formations, such as sandstones,
are encountered near an excavation, impermeable soil layers can be con-
structed from the nearby abundant spoil. Abandoned limestone, sandstone,
10 siltstone, granite, and traprock quarries and open pit mines generally
| require more extensive improvements because they are in permeable or
often open-fractured formations. The pollution potential of sand and
gravel pits is great, and worked-out pits consequently require extensive
investigation and probably expensive improvements to control gas movement
i and water pollution.
fll Marsh and tidal lands may also be filled, but they are less desirable
from an ecological point of view. They have little value as real estate,
but possess considerable ecological value as nesting and feeding grounds
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for wildlife. Filling of such areas requires, however, the permanent
lowering of the groundwater or the raising of the ground surface to keep
organic and soluble solid waste from being deposited in standing water. H
Roads for collection vehicles are also needed, and cover material generally
has to be hauled in.
REFERENCE
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Black, R. J., and A. M. Barnes. Effect of earth cover on fly H
emergence from sanitary landfills. Public Works, 89(2):91-94, ^
Feb. 1958. Condensed and reprinted as Fly emergence control in
sanitary landfills. Refuse Removal Journal, 1(5) :13, 25, May 1958.
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CHAPTER V
SANITARY LANDFILL DESIGN
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The designing of a sanitary landfill calls for developing a detailed
description and plans that outline the steps to be taken to provide for
the safe, efficient disposal of the quantities and types of solid wastes
that are expected to be received. The designer outlines volume require-
ments, site improvements (clearing of the land, construction of roadways
^^ and buildings, fencing, utilities), and all the equipment necessary for
^" day-to-day operations of the specific landfilling method involved. He
also provides for controlling water pollution and the movement of de-
composition gas. The sanitary landfill designer should also recommend
a specific use of the site after landfilling is completed. Finally,
_ he should determine capital costs and projected operating expenditures
for the estimated life of the project.
IH Volume Requirements
II If the rate at which solid wastes are collected and the capacity
_ of the proposed site are known, its useful life can be estimated. The
^^ ratio of solid waste to cover material volume usually ranges between
4:1 and 3:1; it is, however, influenced by the thickness of the cover
used and cell configuration. If cover material is not excavated from
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the fill site, thK ratio may be compared with the volume of compacted
soil waste and the capacity of a site determined (Figure 6). For example,
a town having a 10,000 population and a per capita collection rate of
5 lb per day must dispose of, in 1 year, 11 acre-ft of solid waste if
it is compacted to 1,000 lb per cu yd. If it were compacted to only iH
600 lb per cu yd, the volume disposed of in 1 year would occupy 19 acre-
ft. The volume of soil required for the 1,000-lb density at a solid
waste-to-cover ratio of 4:1 would be 2.75 acre-ft; the 600-lb density H
waste would need 4.7b acre-ft. A density of 800 lb per cu yd is easily
achievable if the compacting of a representative municipal waste is
involved. A density of 1,000 lb per cu yd can usually be obtained if
the waste is spread and compacted according to procedures described in
Chapter VI .
The number of tons to be disposed of at a proposed sanitary land-
fill can be estimated from data recorded when solid wastes are delivered
to disposal sites. The daily volume of compacted solid waste can then
be easily determined for a large community (Figure 7) or for a small
community (Figure 8). The volume of soil required to cover each day's H
waste is then estimated by using the appropriate solid waste-to-cover
ra t i o .
The terms used to report densities at landfills can be confusing.
Solid waste density (field density) is the weight of a unit volume of
solid waste in place. Landfill density is the weight of a unit volume H
of in-place solid waste divided by the volume of solid waste and its
cover material. Both methods of reporting density are usually expressed
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FIGURE 6
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2 4 6 8 10
SOLID WASTE COLLECTED (pounds/capita/calendar day)
Yearly volume of compacted solid waste for a
community of 10,000 people
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SOLID WASTE DISPOSED DAILY (tons/day)
500
1000
FIGURE 7. Daily volume of compacted solid waste from
large communities.
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SOLID WASTE DISPOSED DAILY'(tons/day)
FIGURE a. Daily volume of compacted solid wa'ste frpm
small communities.
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as pounds per cubic yard, on an in-place weight basis, including moisture, H
at time of the test, unless otherwise stated.
Site Improvements
The plan for a sanitary landfill should prescribe how the site will
be improved to provide an orderly and sanitary operation. This may simply
involve the clearing of shrubs, trees, and other obstacles that could
hinder vehicle travel and landfilling operations or it could involve H
the construction of buildings, roads, and utilities. M
Clearing and Grubbing. Trees and brush that hinder landfill equipment
or collection vehicles must be removed. Trees that cannot be pushed H
over should be cut as close as possible to the ground so that the stumps
do not hinder compaction or obstruct vehicles. Brush and tall grass |
in working areas can be rolled over or grubbed. A large site should »
be cleared in increments to avoid erosion and scarring of the land. If
possible, natural windbreaks and green belts of trees or brush should H
be left in strategic areas to improve appearance and operation. Measures
for minimizing erosion and sedimentation problems are outlined in the ||
publication Community Action Guidebook for Soil Erosion and Sediment
Control . *
I
Roads. Permanent roads should be provided from the public road flj
system to the site. A large site may have to have permanent roads that
lead from its entrance to the vicinity of the working area. They should |
be designed to support the anticipated volume of truck traffic. In general, _
the roadway should consist of two lanes (total minimum width, 24 ft),
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^ for two-way traffic. Grades should not exceed equipment J imitations.
For loaded vehicles, most uphill grades should be less than 7 percent
II and downhill grades less than 10. Road alignments and pavement designs
have been adequately discussed elsewhere.2'3 The initial cost of
H permanent roads is higher than that of temporary roads, but the savings
M in equipment repair and maintenance could justify the building of
^ permanent, on-site roads.
Temporary roads are normally used to deliver wastes to the working
face from the permanent road system because the location of the working
^ face is constantly changing. Temporary roads may be constructed by com-
« pacting the natural soil present and by controlling drainage or by
topping them with a layer of a tractive material, such as gravel, crushed
stone, cinders, broken concrete, mortar, or bricks. Lime, cement, or
asphalt binders may make such roads more serviceable.
|| If fewer than 25 round trips per day to the landfill are expected,
« a graded and compacted soil will usually suffice. More than 50 round
trips per day generally justifies the use of calcium chloride as a dust
inhibitor or such binder materials as soil cement or asphalt. A base
course plus a binder is desirable if more than 100-150 round trips per
|§ day are anticipated.
*jm Scales . Recording the weights of solid waste delivered to a site
can help regulate and control the sanitary landfill operation as well
as the solid waste collection system that serves it.
The scale type and size used will depend on the scope of the operation.
|| Portable scales may suffice for a small site, while an elaborate system
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employing load cells, electronic relays, and printed output may be needed flj
at a large sanitary landfill. Highly automated electronic scales and
recorders cost more than a portable, simple beam scale, but their use H
may often be justified because they are faster and more accurate. The
platform or scale deck may be constructed of wood, steel, or concrete.
The first type is the least expensive, but also the least durable.
The scale should be able to weigh the largest vehicle that will
use the landfill on a routine basis; 30 tons is usually adequate. Gen-
erally, the platform should be long enough to simultaneously weigh all
axles. Separate axle-loading scales (portable versions) are the cheapest,
but they are less accurate and slower operating. The scale platform |B
should be 10 by 3^ ft to weigh most collection vehicles. A 50-ft plat-
form will accommodate most trucks with trailers.
The accuracy and internal mechanism of the scale and the recording ^
device should meet the commercial requirements imposed by the State and
any other jurisdiction involved, particularly if user fees are based
on weight. Recommended scale requirements have been outlined by the
National Bureau of Standards.1*
Since weights are seldom recorded closer than to the nearest tenth ^_
of a ton and most applied loads are between 8 and 14 tons, a scale accuracy ^*
of +_ 1.0 percent is acceptable. All scales should be periodically checked Mj
and certified as to standard accuracy.
Both mechanical and electronic scales should be tested quarterly
under load. The inspection should include: (l) checking for a change ^_
in indicated weight as a heavy load is moved from the front to the back ^*
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of the scale; (2) observing the action of the dial during weighing for
an irregularity or "catch" in its motion; (3) using test weights.
mm BuiIdings. A building is needed for office space and employee
facilities at all but the smallest landfill; it can also serve as a scale
^| house. Since a landfill operates in wet and cold weather, some protec-
tion from the elements should be provided. Operational records may also
H be kept at a large site. Sanitary facilities should be provided for
mm both landfill and collection personnel. A building should also be pro-
vided for equipment storage and maintenance.
Wm Buildings on sites that will be used for less than 10 years should
be temporary types and, preferably, be movable. The design and location
of all structures should consider gas movement and differential settle-
mm ment caused by the decomposing solid waste.
Uti1i ties. All sanitary landfill sites should have electrical,
water, and sanitary services. Remote sites may have to extend existing
services or use acceptable substitutes. Portable chemical toilets can
II be used to avoid the high cost of extending sewer lines, potable water
^ may be trucked in, and an electric generator may be used instead of having
power lines run into the site.
II Water should be available for drinking, fire fighting, dust control,
and employee sanitation. A sewer line may be called for, especially
|| at large sites and those where leachate is collected and treated with
M domestic wastewater. Telephone or radio communications are also desirable.
Fencing. Peripheral and litter fences are commonly needed at sanitary
landfills. The first type is used to control or limit access, keep out
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children, dogs, and other large animals, screen the landfill, and de-
lineate the property line. If vandalism and trespassing are to be dis- JH
couraged, a 6-ft high fence topped with three strands of barbed wire M
projecting at a ^5° angle is desirable. A wooden fence or a hedge may
be used to screen the operation from view. ^1
Litter fences are used to control blowing paper in the immediate
vicinity of the working face. As a general rule, trench operations re- ^|
quire less litter fencing because the solid waste tends to be confined M
within the walls of the trench. At a very windy trench site, a 4-ft
snow fence will usually suffice. Blowing paper is more of a problem ^1
in an area operation; 6- to 10-ft litter fences are often needed. Some
litter fences have been specially designed and fabricated (Figure 9).
Since the location of the working face shifts frequently, litter fences
should be movable.
Control of Surface Water Bi
Surface water courses should be diverted from the sanitary landfill. H
Pipes may be used in gullies, ravines, and canyons that are being filled ^^
to transmit upland drainage through the site and open channels employed
to divert runoff from surrounding areas (Figure 10). Sump pumps may II
also be used. Because of operating and maintenance requirements, the
use of mechanical equipment for water control is, however, strongly dis- gg
couraged unless the control is needed only temporarily. If trenches ^
or depressions are being filled, collection sumps and pumps may be used
to keep them from flooding. Equipment sizes can be determined by analyzing H
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storm and flood records covering about a 50-year period. Counseling
J| and guidance in planning water management measures are available tnrough
M local soil conservation districts upon request. A landfill located in
a flood plain should be protected by impervious dikes and liners. The
top of the dike should be wide enough for maintenance work to be carried
out and may be designed for use by collection and landfill vehicles.
ff The top cover material of a landfill should be graded to allow run-
M off of rainfall. The grade of the cover will depend on the material's
^^ ability to resist erosion and the planned use of the completed site.
H Portable or permanent drainage channels may be constructed to intercept
and remove runoff water. Low-cost, portable drainage channels can be
11 made by bolting together half-sections of corrugated steel pipes. Sur-
M face water that runs off stockpiled cover material may contain suspended
solids and should not be allowed to enter watercourses unless it has
been ponded to remove settleable solids.
| Groundwater Protection
_ It is a basic premise that groundwater and the deposited solid waste
not be allowed to interact. It is unwise to assume that a leachate will
II be diluted in groundwater because very little mixing occurs in an aquifer
since the groundwater flow there is usually laminar.
When issuing permits or certificates, many States require that ground-
^ water and deposited solid wastes be 2 to 30 ft apart. Generally, a 5-ft
separation will remove enough readily decomposed organ!cs and coliform
bacteria to make the liquid bacteriologically safe.5'6 On the other
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hand, mineral pollutants can travel long distances through soil or rock
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formations. In addition to other considerations, the sanitary landfill
designer must evaluate the: (l) current and projected use of the water
resources of the area; (2) effect of leachate on groundwater quality;
(3) direction of groundwater movement; (k) interrelationship of this
aquifer with other aquifers and surface waters. 9M
Groundwater mounds, rises in the piezometric level of an aquifer
in a recharge area, have been found at several landfills.7 The mounds H
are reported to be up to 5 ft above the surrounding groundwater level,
and they have intersected deposited solid waste. The investigators be-
lieve the water table probably rose because: (1) the permeability of
the landfill's soil boundary decreased as a result of excavation and
reworking; (2) more water infiltrated through the cover material and
solid waste than through the undisturbed soils of the surrounding area.7
If a groundwater mound intersects the solid waste, leachate will
undoubtedly enter the groundwater and may emerge as a spring around the M
toe of the fill where the groundwater table intersects the ground surface.
Both surface and groundwaters may, therefore, be endangered if a mound ^1
forms .
An impermeable liner may be employed to control the movement of
fluids. One of the most commonly used is a we 1 1 -compacted natural clay mm
soil, usually constructed as a membrane 1 to 3 ft thick. It must, however,
be kept moist. If sufficient clay soil is not available locally, natural
clay additives, such as montmor i 1 loni te, may be disked into it to form
an effective liner. The use of additives requires evaluation to determine
optimum types and amounts.
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Since synthetic liners have been used to construct wastewater-
holding-and-treatment ponds, they may have an application in solid waste
disposal operations. They are usually made of butyl rubber, polyethylene,
or polyvi nylchlori de and are installed in multiple layers. (if the move-
IB ment of both gas and leachate is to be controlled, polyvinylchloride
| should work better than polyethylene because it is less permeable by
gas.) The membranes must be put down carefully to avoid punctures, and
layers of soil (usually sand) must be placed on both sides of them.
Asphalt liners, which have been used to reduce seepage from canals and
mi ditches, may also have an application in a solid waste disposal operation.
|M The use of an impermeable barrier requires that some method be pro-
vided for removal of the contained fluid. If a natural ravine or canyon
is involved, the removal point should be the downstream end of the filled
area. The fluid in a bowl -shaped liner could be pumped by a well or
H series of wells or it could exit through gravity outlets in the bottom
mu of the liner. In the latter case, the pipes should be sloped 1/8 to
1/4 in. per ft.
^1 It is often possible to permanently or temporarily lower the ground-
water in free-draining, gravelly, and sandy soils. Drains, canals, and
|| ditches are frequently used to intercept the groundwater and channel
it to surface water or recharge area at a lower elevation. Doing this
generally requires that the designer have a thorough knowledge of the
soil permeabilities and the groundwater flow system in the area. It is
inadvisable to use temporary methods, such as wells, to lower the water
H table because it will rise after pumping ceases, and the waste will be
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Inundated. It is well to recognize that highly permeable soils that ^_
can be readily drained by ditching or pumping will offer equally little
resistance to the movement of leachate from the decomposing solid waste.
Even though groundwater can be kept from coming into direct contact with
the solid waste, in most climates infiltrated surface water will probably JJ
enter the solid waste eventually, cause leaching, and then percolate ^
through the underlying porous soil to enter the lowered groundwater. ^^
It is advisable, therefore, to view sites in highly permeable material II
with extreme caution.
Little work has been done to determine the types and costs of ||
leachate treatment. Analysis of leachate samples from a few landfills ^H
and laboratory lysimeters indicates that leachate is a complex liquid
waste and has variable characteristics. Since most of the contaminants B
in leachate are water soluble, conventional biological and chemical treat-
ment methods are probably required and, hopefully, will prove effective. jjj^
To help establish if a landfill is creating a groundwater and surface ^_
water pollution problem, a series of observation wells and sampling sta-
ttons can be used to periodically monitor the water quality. Data on II
the upstream or uncontaminated water and downstream water quality are
necessary to evaluate the later pollution potential.
Gas Movement Control
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An important part of sanitary landfill design is controlling the
movement of decomposition gases, mainly carbon dioxide and methane. Traces
of hydrogen sulfide and other odorous gases may also be involved.
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Methane (CH,) is a colorless, odorless gas that is highly explosive
in concentrations of 5 to 15 percent when in the presence of oxygen. In
H a few instances, methane gas has moved from a landfill and accumulated
in explosive concentrations in sewer lines and nearby buildings. Gas
H from landfills has also killed nearby vegetation, presumably by excluding
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oxygen from the root zone. Carbon dioxide (CO-) is also a colorless,
odorless gas, but it does not support combustion. It is approximately
1.5 times as heavy as air and is soluble in water. The C07 reacts to
a limited extent to form carbonic acid (hLCO_) , which can dissolve min-
eral matter, particularly carbonates, in refuse, soil, and rock. If this
occurs, the mineral content or hardness of the water increases, as has
been noted at wells located near landfills and dumps.
In general, no problems arise when landfill gas can disperse into
the atmosphere. If the fill has a relatively impermeable cover, however,
I the methane will try to vent into the atmosphere by moving laterally
through a more permeable material.
The natura1 soil, hydrologic, and geologic conditions of the site
may provide control of gas movement. If not, methods based on controlling
gas permeability can be constructed. The following have been used or
H are considered possible.
Permeable Methods. Lateral gas movement can be prevented by using
a material that isunder all circumstances more permeable than the
H surrounding soil; gravel vents or gravel-filled trenches have been em-
ployed (Figure 11). Preferably, the trenches should be somewhat deeper
than the fill to make sure they intercept all lateral gas flow. The
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slope
Figure 31.
Gravel
58
vents
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filter material should be graded to avoid infiltration and clogging by
adjacent soil carried in by water. If possible, the trench should be
built so that it drains naturally; field tile is often placed in the
bottom of the trench. The surface of gravel trenches should be kept free
i of soil and vegetation because they retain moisture and hinder venting.
In another method, vent pipes are inserted through a relatively im-
permeable top cover (Figure 12). Collecting laterals placed in shallow
gravel trenches within or on top of the waste can be connected to the
vertical riser. The sizes and s pacings required have not been established,
i but they depend on the rate of gas production, total weight of solid waste,
| and the gas permeability of both the cover and the surrounding soil. In
some cases, vertical risers have been used to burn the gas. Pipe vents
should not be located near buildings, but if this is unavoidable, they
should discharge above the roof line.
i Pumped exhaust wells may be used for gas venting. In this method,
pipe vents are attached to the line of a suction pump to create differ-
ential driving pressure for gas movement. This method is costly and re-
quires frequent maintenance.
Impermeable Methods. The movement of gas through soils can be con-
Hi trolled by using materials that are more impermeable to it than the
surrounding soil. An impermeable barrier can be used to contain the gas
and vent it through the top cover or simply to block the flow of gas.
The most common method, and possibly the most practical, calls for
the use of compacted clay. The material must, however, be kept moist,
H otherwise it could shrink and crack. (Other fine-grained soils may also
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_ be used, with the same stipulation.) The clay can be placed as a liner
^ in an excavation or installed as a curtain wall to block underground gas
H flow (Figure 13)- A clay layer 18 to ^8 in. thick is probably adequate,
but it should be continuous and not be penetrated by solid waste or out-
II croppings of the surrounding soil or rocks. The liner should be con-
_ structed as the fill progresses, because prolonged exposure to air will
^* dry the clay and cause it to shrink and crack.
H| The use of synthetic membranes was described in the section on Ground-
water Protection.
Landfill ing Methods
The designer of a sanitary landfill should prescribe the method of
flj construction and the procedures to be followed in disposing of the solid
waste, because there is no "best method" for all sites. The method
jjl selected depends on the physical conditions involved and the amount and
_ types of solid waste to be handled.
The two basic landfill ing methods are trench and area; other ap-
H| preaches are only modifications. In general, the trench method is used
when the groundwater is low and the soil is more than 6 ft deep. It is
£ best employed on flat or gently rolling land. The area method can be
_ followed on most topographies and is often used if large quantities of
solid waste must be disposed of. At many sites, a combination of the
Bj two methods is used.
Cell Construction and Cover Material. The building block common
H to both methods is the cell. All the solid waste received is spread and
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compacted in layers within a confined area. At the end of each working
day, or more frequently, it is covered completely with a thin, continuous
H layer of soil, which is then also compacted. The compacted waste and
soil cover constitute a cell. A series of adjoining cells all of the
i same height makes up a lift (Figure lA). The completed fill consists
of one or more lifts.
The dimensions of the cell are determined by the volume of the com-
pacted waste, and this, in turn, depends on the density of the in-place
solid waste. The field density of most compacted solid waste within the
cell should be at least 800 Ib per cu yd. (It should be considerably
higher if large amounts of demolition rubble, glass, and wel1-compacted
inorganic materials are present.) The 800-lb figure may be difficult
to achieve if brushes from bushes and trees, plastic turnings, synthetic
fibres, or rubber powder and trimmings predominate. Because these ma-
i terials normally tend to rebound when the compacting load is released,
j they should be spread in layers up to 2 ft thick, then covered with 6
in. of soil. Over this, mixed solid waste should be spread and compacted.
The overlying weight keeps the fluffy or elastic materials reasonably
compressed.
An orderly operation should be achieved by maintaining a narrow work-
IB ing face (that portion of the uncompleted cell on which additional waste
is spread and compacted). It should be wide enough to prevent a backlog
of trucks waiting to dump, but not be so wide that it becomes impractical
to manage properlynever over 150 ft.
H No hard-and-fast rule can be laid down regarding the proper height
of a cell. Some designers think it should be 8 ft or less, presumably
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s^$>^^^
Original Ground
FIGURE 14. SANITARY LANDFILL CONSTRUCTION
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M because this height will not cause severe settlement problems. On the
other hand, if a multiple lift operation is involved and all the cells
are built to the same height, whether 8 or 16 ft, total settlement should
not differ significantly. If land and cover material are readily avail-
B able, an 8-ft height restriction might be appropriate, but heights up
M to 30 ft are common in large operations. Rather than deciding on an
arbitrary figure, the designer should attempt to keep cover material
^B volume at a minumum while adequately disposing of as much waste as possible.
Cover material volume requirements are dependent on the surface area
Jj of waste to be covered and the thickness of soil needed to perform par-
^_ ticular functions. As might be expected, cell configuration can greatly
affect the volume of cover material needed. The surface area to be
^1 covered should therefore be kept minimal.
In general, the cell should be about square, and its sides should
fjj be sloped as steeply as practical operation will permit. Side slopes
^ of 20° to 30° will not only keep the surface area, and hence the cover
material volume, at a minimum but will also aid in shredding and obtaining
j good compaction of solid waste, particularly if it is spread in layers
not greater than 2-ft thick and worked from the bottom of the slope to
| the top.
^ Trench Method. Waste is spread and compacted in an excavated trench.
Cover material, which is taken from the spoil of the excavation, is spread
H
and compacted over the waste to form the basic cell structure (Figure
15). In this method, cover material is readily available as a result
of the excavation. Spoil material not needed for daily cover may be
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EARTH COVER OBTAINED
BY EXCAVATION
IN TRENCH
-COMPACTED
SOLID WASTE
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FIGURE ? 5.
TRENCH METHOD.
The waste collection truck deposits its
load into the trench where the bulldozer
spreads and compacts it. At the end of
the day soil is excavated from the future
trench and used as the daily cover
material.
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stockpiled and later used as a cover for an area fill operation designed
|| for the top of the completed trench fill operation.
mm Cohesive soils, such as glacial till or clayey silt, are desirable
for use in a trench operation because the walls between the trenches can
be thin and nearly vertical. The trenches can, therefore, be spaced very
closely. Weather and the length of time the trench is to remain open
H also affect soil stability and must, therefore, be considered when the
mm slope of the trench walls is being designed. If the trenches are aligned
perpendicularly to the prevailing wind, this can greatly reduce the amount
of blowing litter. The bottom of the trench should be slightly sloped
for drainage, and provision should be made for surface water to run off
| at the low end of the trench. Excavated soil can be used to form a tem-
mm porary berm on the sides of the trench to divert surface water.
The trench can be as deep as soil and groundwater conditions safely
allow, and it should be at least twice as wide as any compacting equipment
that will work in it. The equipment at the site may excavate the trench
| continuously at a rate geared to landfill ing requirements. At small
mm sites, excavation may be done on a contract basis.
Area Method. In this method, the waste is spread and compacted on
the natural surface of the ground, and cover material is spread and com-
pacted over it (Figure 16). The area method is used on flat or gently
| sloping land and also in quarries, strip mines, ravines, valleys, or other
mm land depressions.
Combination Methods. A sanitary landfill does not need to be oper-
ated by using only the area or trench method. Combinations of the two
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PORTABLE FENCE TO
CATCH BLOWING
PAPER
FIGURE
AREA METHOD.
The bulldozer spreads and compacts solid
wastes. The scraper (foreground) is used
to haul the cover material at the end of
the day's operations. Note the portable.
fence that catches any blowing debris.
This is used with any landfill method.
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_ are possible, and flexibility is, therefore, one of sanitary landfi 1 1 ing's
greatest assets. The methods used can be varied according to the con-
straints of a particular site.
One common variation is the progressive slope or ramp method, in
|H which the solid waste is spread and compacted on a slope. Cover material
« is obtained directly in front of the working face and compacted on the
waste (Figure 17). In this way, a small excavation is made for a portion
of the next day's waste. This technique allows for more efficient use
of the disposal site when a single lift is constructed than the area
|| method does, because cover does not have to be imported, and a portion
_ of the waste is deposited below the original surface.
Both methods might have to be used at the same site if an extremely
H large amount of solid waste must be disposed of. For example, at a site
with a thick soil zone over much of it but with only a shallow soil over
|| the remainder, the designer would use the trench method in the thick soil
M zone and use the extra spoil material obtained to carry out the area
method over the rest of the site. When a site has been developed by
H either method, additional lifts can be constructed using the area method
by having cover material hauled in.
If The final surface of the completed landfill should be so designed
_ that ponding of precipitation does not occur. Settlement must, therefore,
be considered. Grading of the final surface should induce drainage but
H not be so extreme that the cover material is eroded. Side slopes of the
completed surface should be 3 to 1 or flatter to minimize maintenance.
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X! CO ?H
EH X! -H
CU 5
«J ft
fft w
TO *O
C fc CO
o o ra
ra 3
o
0 XI tQ
4i 43 iH
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cd rt C
D. T3
X! j CO fn
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rH -H CO 0)
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_ Finally, the designer should consider completing the sanitary land-'
fill in phases so that portions of it can be used as parks and playgrounds,
flj while other parts are still accepting solid wastes.
j| Summary of Design Considerations
_ The final design of a sanitary landfill should describe in detail:
(l) all employee and operational facilities; (2) operational procedures
II and their sequence, equipment, and manpower requirements; (3) the pollu-
tion potential and methods of controlling it; (4) the final grade and
planned use of the completed fill; (5) cost estimates for acquiring,
_ developing, and operating the proposed site.
The designer should also provide a map that shows the location of
the site and the area to be served and a topographic map covering the
area out to 1,000 ft from the site. Additional maps and cross-sections
should also be included that show the planned stages of filling (start-
up, intermediate lifts, and completion). They should present the details
of:
1. Roads on and off the site;
2. Bui Idings ;
3* Utilities above and below ground;
A. Scales;
5. Fire protection facilities;
6. Surface drainage (natural and constructed) and groundwater;
7- Profiles of soil and bedrock;
8. Leachate collection and treatment facilities;
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9. Gas control devices;
10. Buildings within 1,000 ft of property (residential, commercial,
agricultural;
11. Streams, lakes, springs and wells within 1,000 ft;
12. Borrow areas and volume of material available; H
13- Direction of prevailing wind;
]k. Areas to be landfilled, including special waste areas, and
limitations on types of waste that may be disposed of;
15. Sequence of filling;
16. Entrance to facility;
17. Peripheral fencing;
18. Landscaping;
19. Completed use.
REFERENCES
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1. Community Action Guidebook for Soil Erosion and Sediment Control.
The National Association of Counties Research Foundation. ^*
2. Hay, W. H. Transportation Engineering. John Wiley 6 Sons, Inc.
New York, 1961 . H
3. Oglesby, C. H., and L. I. Hewes. Highway Engineering. John Wiley M
6 Sons, Inc. New York, 1963.
b. U.S. National Bureau of Standards. Specifications, tolerances, and
other technical requirements for commercial weighing and measuring
devices adopted by National Conference on Weights and Measures.
Handbook M. 3rd ed. Washington, U.S. Government Printing Office,
1965. 178 p.
5. Waste water reclamation in relation to ground water pollution.
California State Water Quality Control Board, Publication No. 2k.
Sacramento, 1953*
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6. Anderson, D. R., W. D. Bishop, and H. F. Ludwig. Percolation of
citrus wastes through soil. j_n_ Proceedings of the 21st Industrial
Waste Conference, Purdue University, Lafayette, Indiana, 1966.
7. Hughes, G. M., R. A. Landon, and R. N. Farvolden. Hydrogeology of
solid waste disposal sites in northeastern Illinois; an interim
report on a solid waste demonstration project. U.S. Department
of Health, Education, and Welfare, Cincinnati, 1969. 137 p.
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CHAPTER VI
SANITARY LANDFILL OPERATION
The best designed disposal facility will be of little value unless
it is constructed and operated as prescribed. This is especially true ^
of a sanitary landfill because it is under construction up to the day ^^
the last particle of solid waste is disposed of. Constructing the sani-
tary landfill on a daily basis in accordance with the design should be
unequivocally required in an operations plan. H
An operations plan is essentially the specification for construction ^
and it should contain all items required to construct the sanitary land- ^
fill. It should describe: (1) hours of operation; (2) measuring pro- Hj
cedures; (3) traffic flow and unloading procedures; (k) designation of
specific disposal areas and methods of handling and compacting various Ij
solid wastes; (5) placement of cover material; (6) maintenance procedures; ^
(7) adverse weather operations; (8) fire control; (9) litter control; "
(10) salvaging operations, if permitted. H
Proper operation calls for drawing up a comprehensive plan that
spells out routine procedures and anticipates abnormal situations. It
must also provide continuity of activities even when personnel changes ^_
occur. New supervisors and personnel responsible for solid waste dis-
posal must know what is being done at the landfill and why. The plan
must, however, remain open for revision when necessary. Changes should
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be noted, and the rationale behind them explained. New personnel will
i benefit from the experience of others, and continuity of operations will
be preserved.
The plan should also be used as a tool in training employees, de-
ll fining their jobs, and giving them an insight into the work of others.
In this manner, the employee will more fully understand the overall
operation, and he may be able to perform other duties in an emergency.
H Hours of Operation
II The hours a sanitary landfill operates depends mainly on when the
wastes are delivered, and generally this is done during normal working
hours. In large cities, however, waste collection systems sometimes
operate 2k hr a day. In this case, a site should not be located In a
residential area. The usual landfill is open 5 to 6 days a week and 8
to 10 hr a day.
_ The hours of operation should be posted on a sign at the landfill
entrance. It should also indicate what wastes are not accepted; fees
II charged; and the name, address, and telephone number of the operating
body (sanitation district, private company, etc.). All this information
|H must be kept current. Fees are usually levied on a cost -per- ton basis
_ for large loads and on a flat fee basis for small amounts brought to the
site by homeowners. The sanitary landfill should be open only when op-
erators are on duty.
If it is anticipated that waste will be brought to a disposal site
at other times, a large container should be placed outside the site en-
trance.
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Weighing the Solid Waste «
The efficiency of filling and compacting operations can be adequately
judged if the amount of solid waste delivered, the quantity of cover ma-
terial used, and the volume occupied by the landfilled solid waste and H
cover are known. (Weighing is the most reliable means of measurement.)
These values are also used to determine the density of the fill and to
estimate the amount of settlement that will probably occur. Weight and ^^
volume data can also be used in designing new landfills and predicting
the remaining capacity of currently operating landfills.
The number of vehicles that can be weighed in a unit of time will
vary. An experienced weighmaster is able to record manually, for short
periods of time, the net weight and types of material delivered at a rate
of 60 trucks per hr, but it is extremely taxing to maintain this pace »
for long periods. A highly automated weighing procedure can easily ac- II
commodate over 60 trucks per hr, record more data, require less super-
vision, and be more accurate. Landfills disposing of 1,000 tons or more H
per day will usually require two or more automatic scales. Truck scales ^^
require little maintenance if inspected and maintained as recommended ^
by their manufacturers. IB
Although a seemingly simple operation, weighing presents many prob-
lems. To ensure that all trucks are weighed, vehicle-handling controls H
and accounting techniques must be developed. Techniques being used in-
elude a two-gate system (one at the front and one at the back of the
scale) that locks a truck on the scale until weighed, one-way exit barri-
cades, signal lights, curbing, alarms, and numerous automated recording
devices. H
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_ If a truck is not properly positioned on the platform (one or more
axles off) the weight recorded will be wrong. Suitable curbing, markings,
H elevated transverse bumps, or extra long scales can reduce or prevent
unintentional misplacement of vehicles on the scale.
H Dirt, water, snow, and ice may accumulate on and under the deck of
^_ the scale and cause it to wear and rust, lead to hazardous driving con-
^ ditions, and generate weighing errors.
B Traffic Flow and Unloading
H Traffic flow on the site can affect the efficiency of daily opera-
tions. Traffic should be allowed to bypass the scale only if it is
i inoperative. Haphazard routing between the scale and the disposal area
can lead to indiscriminate dumping and cause accidents. Pylons, barri-
cades, guardrails, and traffic signs can be used to direct traffic.
Large sites may need posted maps to direct trucks. If separate working
areas are established for different types of wastes, signs should be used
B to direct drivers to the appropriate disposal areas.
Wastes are delivered to a landfill in vehicles that range from auto-
mobiles to large transfer trailers. Operationally, they comprise groups
H that are unloaded manually or mechanically. The two categories are es-
tablished because of the difference in time it takes to unload the waste
at the working face. If large numbers of manually unloaded vehicles must
be handled, special procedures may be necessary.
Mechanically discharging vehicles include dump trucks, packer-type
H collection trucks, tank trucks, and open or closed body trucks equipped
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with a movable bulkhead that requires the use of a crawler dozer or mm
loader. These vehicles are capable of rapidly discharging their waste
loads and should be routed directly to the working face without delay.
Manually discharging vehicles take more time to unload and should
not be permitted to slow the unloading of vehicles that can discharge
mechanically. Many of the drivers will not be familiar with the land-
fill operation and will require close supervision. If a large number
of manually discharging vehicles is involved, a separate unloading area
may be necessary to avoid delaying other vehicles.
Scavenging should not be permitted, and no vehicle should be left |
unattended. Waste should be deposited at the toe of the working face,
because it can be compacted better there since it is worked up the slope
rather than down. If it is necessary to discharge solid wastes at the
top of the slope, as in a narrow trench operation, telephone poles or
similar objects should be emplaced to warn drivers .that they are near H
its edge. The unloading area should be as level as practical for dump
trucks and other vehicles having high centers of gravity in the raised
position. H
Handl ing of Wastes
Wastes come from residences, commercial establishments, institutions, mm
municipal operations, industries, and farms. Some may require special
methods of handling and burial. The landfill designer should know all
the types that will likely be involved and make provision for their dis-
posal. Materials that cannot be safely buried should be excluded. |
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_ Residential, Commercial, and Industrial Wastes. These wastes (ex-
^ elusive of process wastes discussed later) are usually highly compactible.
II They contain a heterogeneous mixture of such materials as paper, cans,
bottles, cardboard and wooden boxes, plastics, lumber, metals, yard
H clippings, food waste, rocks, and soil. When exposed, boxes, plastic
^ and glass containers, tin cans, and brush can be compressed and crushed
under relatively low pressure. In a landfill, however, these easily
compressible items are incorporated within the mass of solid waste. The
mass acts as a cushion and often bridges, thus protecting the relatively
H low-strength materials from being crushed under the load of the compaction
equipment.
Cushioning and bridging can be reduced and greater volume reduction
achieved if the waste is spread in layers less than 2 ft deep and is then
compacted by tracked, rubber tired, or steel wheeled vehicles that pass
over it 2 to 5 times. Solid waste that contains a high percentage of
brush and yard clippings requires more compactive effort. If entire
loads of these items are received, they should be spread and compacted
near the bottom of the cell so that less resilient wastes can be compacted
on top.
H The equipment operator should try to develop the working face on
a slope between 20° and 30° (Figure 18). Waste is spread against the
slope, and the machine moves up and down the slope, thus tearing and
compacting the waste and eliminating voids. The equipment operator should
make repeated passes until he no longer can detect that the surface of
the waste layer is being depressed more than it is rebounding.
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STEP I.:.;. SOLID WASTE
FIGURE 18. SPREADING AND COMPACTING SOLID WASTE
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Bulky Wastes. Bulky wastes include car bodies, demolition and con-
struction debris, large appliances, tree stumps, and timbers. Significant
_ volume reduction of construction rubble and stumps by compaction cannot
^^ be achieved, but car bodies, furniture, and appliances can be significantly
H reduced in volume. A small crawler dozer (110 HP and 20,000 Ib, or less)
has greater difficulty in compacting washing machines and auto bodies
£ than would heavy machines, but some volume reduction can be achieved.
_ Such items should be crushed on solid ground and then pushed onto the
" working face, near the bottom of the cell or into a separate disposal
area. Once in place, most bulky items do not degrade (at least not at
a rate comparable to surrounding refuse). Consequently, if bulky items
are incorporated into degradable wastes, uneven settlement will result.
_ Special areas for bulky items should be identified on the final plan of
the completed site. Even though bulky wastes do not usually contain
putrescibles, they should be completely covered at the end of each op-
erating day to eliminate harborage for rats and other pests.
H Selected loads of demolition and construction debris--broken concrete,
^^ asphalt, bricks, and plaster--can be stockpiled and used to construct
on-site roads.
Institutional Wastes. Solid wastes from schools, rest homes, and
hospitals are usually highly compactible and can often be handled in the
H same manner as residential and commercial wastes and are often delivered
along with them. If hospital wastes are delivered separately, they should
be spread immediately, compacted, and enclosed with another layer of waste
or a cover material because they could contain pathogenic organisms.
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Pathological wastes are usually disposed of in a special incinerator, ^m
but if accepted, they should be buried immediately under 1 ft of cover
material. Some States have restrictions on the way such wastes are buried, H
and pertinent State laws should be consulted.
Dead Animals. Dead birds, cats, dogs, horses, and cows are occasion- B
ally delivered to sanitary landfills. The burial method is covered by JM
law in most States. Some require that they be immediately incorporated
into the landfill and covered, others demand that they be placed in a
pit and covered with lime. In general, small animal corpses can be safely
disposed of if placed in a landfill along with other wastes and immedi- |
ately covered. Very large animals are usually dismembered so they can «
be transported to the disposal site. They are then placed in a pit and
covered with 2 ft of compacted soil; this should be graded periodically H
to avoid ponding and settlement, which could be appreciable.
Industrial Process Waste. Because of the wide variety of industrial £
process wastes and their different chemical, physical, and biological «
characteristics, it is difficult to generalize about handling these
wastes. The best source of information concerning their characteristics H
are the industries that produce them. It is extremely important to
evaluate the influence of these wastes on the environment. If an in- Hj
dustrial waste is determined to be unsuitable for disposal at the land- _
fill, it should be excluded and the respective industries notified.
Another important factor, not to be overlooked, is the health and safety H
of landfill personnel.
Industrial wastes delivered to a landfill may be in the form of a H
liquid, semi-liquid, films, sheets, granules, shavings, turnings, powders,
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and defectively manufactured products of all shapes and sizes. Whether-
11 or not these are disposed of in the sanitary landfill depends on the
_ environmental conditions of the site and whether or not they are chemi-
cally and biologically stable. They should not be allowed to pollute
H surface water or groundwater.
Liquids and semi-1iquids, if deemed safe to place in a landfill,
^ should be admixed with relatively dry, absorbent solid waste or they may
_ be disposed of in pits well above the groundwater table. The pit should
be fenced and the gate locked to prevent unauthorized access. Location
of this pit should be recorded in the final plan of the completed site.
Films and other light, fluffy, easily airborne materials can be a
H nusisance at the working face. To avoid littering, they should be covered
_ immediately when deposited at the working face. Spraying them with water
may be helpful, but the detrimental effects of adding water should be
considered.
Large sheets of metal, plastic, or wood can also be nuisances at
J the working face. The equipment operator should align the sheets parallel
_ to one another. Random placement leads to large voids, poor compaction,
and substantial settlement of the completed landfill.
Granules, shavings, turnings, and powders can be health hazards to
operating personnel, nuisances if they become airborne, and very abrasive
H or corrosive to the landfill equipment. These wastes should be covered
immediately.
The workers may have to wear face masks, goggles, or protective
clothing to avoid respiratory, eye, or skin ailments.
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Defectively manufactured products are delivered to the landfill to
keep them off the market. These wastes should be incorporated into the
sanitary landfill immediately so that drivers, helpers, and others at
the working face are not tempted to engage in scavenging. Their doing _
so would violate the manufacturer's trust and, even more importantly,
expose them to injury.
Volatile and Flammable Wastes. Some wastes, such as paints, paint
residues, dry cleaning fluids, and magnesium shavings are volatile or H
flammable. They may be in powder, solid, or liquid form, and they usually
derive from industrial processing or are commercial wastes. If they are
not highly flammable or volatile, they may be admixed with other wastes,
otherwise they should be excluded from the fill or quickly disposed of
in a separate area at the site. If the latter step is taken, the area H
should be clearly marked with warning signs, and its exact location re-
corded in the final plan of the completed site. Under no circumstances
should smoking or open flames be allowed in the vicinity of volatile or
flammable wastes when they are being disposed of.
Water and Wastewater Treatment Plant Sludges. Sludges received
from plants that treat water and wastewater can be disposed of at a sani-
tary landfill. In most cases, they can be placed in the regular part
of the fill, but they should be covered immediately. If their moisture
content Is relatively high, the sludges should be mixed with the other
wastes before being covered to prevent localized leaching. Raw sewage
should be disposed of cautiously, because it may contain concentrated
quantities of pathogenic bacteria and viruses. H
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Incinerator Fly Ash and Residue. Fly ash is a fine participate
i material that has been removed from combustion gases. As more stringent
air pollution control regulations are enforced, the quantity of fly ash
that must be disposed of is expected to increase. Fly ash may be moist
or dry, depending on how it is separated from the gas stream. If it is
dry, water may have to be added to it so that it does not become airborne
and create a nuisance. Covering should take place immediately. Residue
is the solid material that remains after a combustion process ends. The
amount of decomposable organics present in incinerator residue varies
H widely, but few incinerators produce a residue low enough in decomposable
organics to allow it to be used as a daily cover material. When the residue
H dries, the fines can create a dust problem. Because of its moisture and
| food content, residue may have a foul odor and attract flies, birds, and
rodents. Residue of this nature should be incorporated into a sanitary
I landfill.
Pesticide Containers. Pesticide containers may be delivered to land-
Hi fills in agricultural areas. If they are empty, they can be crushed by
j the landfill equipment and disposed of along with other solid wastes.
If they are full or only partially empty, they should be excluded from
the sanitary landfill and stored with proper inspection to avoid environ-
mental insult, pending final detoxification and disposal by incineration
H or pyrolysis under carefully controlled time and temperature conditions.
| Animal Manure. Another waste originating primarily in agricultural
areas is animal manure, which often contains a large amount of hay or
bedding. If the waste is not wet enough to flow, it can be placed in
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the regular part of the fill but should be covered immediately. If the
moisture content is high, the manure should be mixed with dry waste and HI
immediately covered.
Radioactive Wastes and Explosives. Landfills do not accept radio-
active wastes." If any are detected in a delivery, the operator should
isolate the wastes, truck, and driver and contact the proper health au-
thorities. Explosives are rarely delivered to a disposal site, and should
be handled with extreme caution when they are. If they are accepted,
the operations plan should contain a provision that explicitly outlines
handling procedures, and a demolitions expert should be consulted if H
possible. The exact location of the waste should be recorded on the final
plan of the completed site, and security fencing and warning signs should
be erected.
Placement of Cover Material
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The operations plan should specify what soils are to be used as
cover material, where they are to be obtained, and how they are to be
placed over the compacted solid waste. The first two specifications are Hj
determined by the landfill designer after he has evaluated the soil in-
vestigation and the functional requirements of the cover material. Cover H
materials used at a sanitary landfill are classed as daily, intermediate,
and final; the classification depends on the thickness of soil used. This H
"Radioactive wastes are disposed of under the auspices of the U.S.
Atomic Energy Commission.
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« is determined by its susceptibility to wind and water erosion and its
ability to meet certain functional requirements. Guides for using the
different classes are determined by the length of time the cover is to
be exposed to the elements (Table 6). In general, if the cover is to be
B exposed for more than 1 week but less than 1 year, intermediate cover
M should be used. If the cover is to be exposed less than 1 week, daily
cover is sufficient, and if the cover is to be exposed longer than 1 year
final cover should be used. All cover material should be well compacted.
Coarse-grained soils can be compacted to 100 to 135 lb per cu ft, fine-
| grained soils to 70 to 120."
I TABLE 6
APPLICATION OF COVER MATERIAL
_ . , Minimum Exposure
Cover material ... . .. .
thickness time*
Daily 6 in. 0-7 days
Intermediate 1 ft 7~365 days
Final 2 ft > 3&5 days
H *The length of time cover material will be exposed to
erosion by wind and rain.
Dai1y Cover. The important control functions of daily cover are
vector, litter, fire, and moisture. Generally, a minimum compacted thick-
ness of 6 in. of soil will perform these functions. The cover is applied
to the compacted waste at least at the end of each operating day. If
*Unit dry weight of compacted soil at optimum moisture content for
Standard AASHO compactive effort.
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possible, it should be spread and compacted on the top and sideslopes
as construction of the cell progresses, thus leaving only the working ||
face exposed. At the end of the operating day, the working face is also «
covered. No waste should be exposed, and the cover should be graded to
prevent erosion and to keep water from ponding. H
Intermediate Cover. Functions of intermediate cover are the same
as daily cover but include gas control and possibly service as a road ||j
base. It is applied in the same manner as daily cover, but the minimum _
compacted depth recommended is 1 ft. Periodic grading and compacting "
may be necessary to repair erosion damage and to prevent ponding of water. H
Cracks and depressions may develop because of moisture loss and settlement
of the fill, and periodic maintenance is required.
Final Cover. Final cover serves basically the same functions as ^_
intermediate cover, but it must also support vegetative growth. At a mini- "
mum, 2 ft of soil should be used, compacted into 6-in. thick layers. Such H
factors as soil type and anticipated use of the completed landfill may
require more than 2 ft. jj^
Grading is extremely important, and grades should be specified in
the landfill design. The general topographic layout of the completed
landfill surface is attained by carefully locating solid waste cells, H
but the final cover is graded and compacted to achieve the desired con-
figuration. Water should not be allowed to pond on the landfill surface
and grades should not exceed 2-A percent to prevent the erosion of cover _
material. Sideslopes should be less than 1 vertical to 3 horizontal. "
Preferably, topsoi 1 from the site should be stockpiled and reserved for
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placement on top of the final cover. Since the topsoi1 will be seeded,
it should not be highly compacted.
Maintenance
A properly operated sanitary landfill is distinguished from an open
dump by its appearance. The effectiveness of pollution control measures
also depends on how well the landfill is maintained during construction
^1 and after completion.
Dust is sometimes a problem, especially in dry climates and if the
|i soil is fine-grained. Dust can cause excessive wear of equipment, can
M be a health hazard to personnel on the site, and can be a nuisance if
there are residences or businesses nearby.
H Dust raised from vehicular traffic can be temporarily controlled
by wetting down roads with water or by using a deliquescent chemical,
1 such as calcium chloride, if the relative humidity is over 30 percent.
Calcium chloride may be applied at a rate of O.A to 0.8 Ib per sq yd and
then be admixed with the top 3 in. of the road surface. Frequent applica-
H tions are usually required, because calcium chloride is soluble in water
and is readily leached from the soil surface. Waste oils can also be
used as temporary dust palliatives. Periodic treatment or multiple
« sprayings at a rate of 0.25 to 1.0 gal per sq yd may be necessary. After
several treatments, a packed, oily soil crust usually develops that has
good resistance to traffic abrasion and is moderately resistant to water.
Good penetration by the oil can be expected in more permeable soils.
Clayey soils or tightly knit surfaces may resist penetration, in which
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case it may be desirable to lightly scarify the surface, apply 0.25 to
0.5 gal of oil per sq yd, and compact the surface. Waste oil, water spray-
ing, and calcium chloride treatment are only temporary solutions; heavily H
traveled roads should be covered with bituminous or cementing materials M
to provide a more permanent surface.
One of the most important aspects of maintenance is litter control.
A landfill operator who permits litter to accumulate and spread from the
site is open to warranted public criticism. Public acceptance of proposed H
sanitary landfills will be easier if those under construction are properly ^m
maintained. Blowing litter can be kept at a minimum by maintaining a
small-size working face and covering portions of the cell as they are ^1
constructed. Snow fences can be positioned around the working face to
catch blowing paper and plastic, but unique wind problems may make it (
necessary to fabricate specially designed fencing. All fences used should M
be portable so that they can be kept near the working face. Personnel
should clean up litter periodically every working day, especially near
the close of business. The litter should be placed on the working face
before it is covered.
Equipment used at a landfill requires regular maintenance, and the M
operations plan should establish a routine preventive maintenance program
for all equipment. Information used to develop this program is available H
from the respective manufacturers.
A daily application of cover material prevents problems associated fjj
with rats, flies, and birds. These pests are rarely troublesome at a M
properly operated sanitary landfill.
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Rats are occasionally brought in along with the solid waste delivered.
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When the waste is unloaded the rats seek cover. They are then buried
H when the waste is spread, compacted, and covered. Infrequently, rats es-
cape and seek protection elsewhere. If they then become a nuisance, they
i should be killed by conducting a baiting program that is supervised by
an experienced exterminator. Local inhabitants must be informed of the
baiting program, signs must be erected, and children and pets must be
H kept away from the bait stations. If strong poisons are used, guards
should keep people away. Generally, an anticoagulant poison should be
used over a two-to-three week period. When no more bait is taken, the
extermination program can be terminated. Procedures for using and making
poisoned bait have been developed for employment at disposal sites.^""^
In no case, however, should extermination procedures be substituted for
^^ daily cover. Poisoning is rarely 100 percent effective, and it is only
a short-term solution.
j If fly problems become severe in summer and an insecticide is used,
daily application is necessary since the insecticide particle must impinge
^ on the fly. Effective insecticides are malathion, dichlorvos, naled,
_ dimethoate, Diazinon, fenthion, and ronnel (Table 7). Application of
cover material as the cell is constructed may control flies without using
insecticides.
Birds that are sometimes attracted to landfills can be a nuisance,
a health hazard, and a danger to low-flying aircraft. Various methods,
_ such as cannon fire, have been used to frighten the birds, but they be-
come familiar with the particular noise and rapidly return. Falcons
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have been used with varying success, but they apparently cannot contend
with seagulls. Record
it back over a public
reduce the problem is
ing the troublesome birds' distress call and playing
address system has also failed. The only way to
to make each working face as small as possible
and to cover all wastes as soon as feasible.
Insecticide
Malathion
Dichlorvos
Naled
Dimethoate
Diazinon
Fen th ion
Ronnel
Weather can slow
TABLE 7
INSECTICIDES FOR FLY CONTROL3
(Outdoor space sprays)
Approximate Ib per acre dosage
required for effective kills
(up to 200 ft)
0.6
0.3
0.1-0.2
0.1-0.2
0.3
o.i*
0.4
Weather Conditions
the construction of a sanitary landfill. The
operations plan should provide detailed instructions on how to operate
the landfill during anticipated inclement periods.
In freezing weather, the greatest difficulty is obtaining cover
material. If the frost penetrates below 6 in., crawler dozers or loaders
equipped with hydrauli
c rippers are needed to loosen the soil. If several
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soils are available at the site, well-drained soils, not as susceptible
to freezing as those that are poorly drained, should be reserved for
use as winter cover material. If the frost line goes more than 1 ft
below the surface, cover material should be stockpiled beforehand.
Calcium chloride can be admixed into the soil to prevent freezing, or
it can be covered with tarpaulins or leaves. Tarpaulins should be dark
to adsorb the sun's heat. If the trench construction method is used,
| enough soil should be excavated during warm months to handle the wastes
to be disposed of during freezing weather. The trench bottom should
be sloped to one end to collect rainfall, which should be pumped out
before it freezes.
Rain can cause operational problems. Roads leading from all-weather
access roads to the working face can become a quagmire and prevent col-
lection trucks from unloading. Roads leading to the active working area
should be passable in any kind of weather. Gravel, crushed stone, and
^^ construction and demolition rubble may be applied to the surface. Col-
lection trucks that pick up mud on the site should be cleaned before
I leaving it to keep them from dirtying the public road system.
Fi res
No burning of wastes is permitted at a sanitary landfill, but fires
occur occasionally because of carelessness in the handling of open flames
or because hot wastes are disposed of. The use of daily cover should
keep fire in a cell that is under construction from spreading laterally
H to other cells. All equipment operators should keep a fire extinguisher
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on their machines at all times, since it may be able to put out a small
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fire. If the fire is too large, waste in the burning area must be spread
out so that water can be applied. This is an extremely hazardous chore,
and water should be sprayed on those parts of the machine that come in
contact with the hot wastes. The operations plan should spell out fire-
fighting procedures and sources of water. All landfill personnel should
be thoroughly familiar with these procedures.
A collection truck occasionally arrives carrying burning waste.
It should not be allowed near the working face of the fill but be routed
as quickly as possible to a safe area, away from buildings, where its §
load can be dumped and the fire extinguished.
Salvage and Scavenging ^
Salvaging usable materials from solid waste is laudable in concept,
but it should be allowed only if a sanitary landfill has been designed
to permit this operation and appropriate processing and storage facilities
have been provided. All salvage proposals must be thoroughly evaluated
to determine their economic and practical feasibility. Salvaging is
usually more effectively accomplished at the point where waste is gene-
rated or at specially built plants. The capital and operating costs
of salvage operations at a disposal site are usually high, even if it
is properly designed and operated. If salvaging is practiced, it should
be accomplished at a specially designed facility away from the operating
area of the sanitary landfill. Salvaging should never be practiced at
the working face.
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Scavenging, sorting through waste to recover seemingly valuable
REFERENCES
I
items, must be strictly prohibited. Scavengers are too intent on search-
H ing to notice the approach of spreading and compacting equipment, and
they risk being injured. Moreover, some of the items collected may be
Bi harmful, such as food waste, canned or otherwise; these items may be
contaminated. Vehicles left unattended by scavengers interfere with
operations at the fill.
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1. Brunner, D. R., S. J. Hubbard, D. J. Keller, and J. L. Newton.
Closing open dumps. [Washington, U.S. Government Printing
« Office], 1971. 19 p.
2. Mai Us, A. Handbook of pest control. 3d ed. New York, MacNair-
_ Dorland Company, Inc., I960. p. k6.
3. Publ ic health pesticides. Pest Control, 38(3); 15-5*t. Mar. 1970.
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CHAPTER VI I
EQUIPMENT
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There is a wide variety of equipment available for sanitary landfill
operations. The types selected will depend on the amount and kinds of fl|
solid waste to be landfilled each day and on the operational methods
to be employed at a particular site. Since money spent on equipment H
constitutes a large capital investment and accounts for a large portion _
of operating costs, the selection should be based on a careful evaluation
of the functions to be performed and the cost and ability of various H
machines to meet the needs.
Equipment Functions
Sanitary landfill machines fall into three general functional cate-
gories: (l) those directly involved in handling waste; (2) those used H
to handle cover material; (3) those that perform support functions.
Waste Handl ing. The practical and safe disposal of solid waste |
is the primary objective of a sanitary landfill. Although the handling _
of solid waste at a landfill site resembles an earthmoving operation, ^
differences exist that require special consideration. Solid waste is
less dense, more compactible, and more heterogeneous than earth. Spread-
ing a given volume of solid waste requires less energy than an equal £
amount of soi 1 . . _
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H Because of its size, strength, and shape, solid waste is not as
conducive as soils to compaction by vibration. In the main, solid waste
H is compacted by the compressive forces developed by the overall massive
loading of a landfill machine. If maximum compaction is desired, a large,
H heavy machine that is operated in accordance with the recommendations
contained in Chapter VI will give better results than a light machine.
Since repeated loading of the solid waste improves its compaction, enough
machines should be available that 2 to 5 compaction passes can be made
during the operating day. If it is not possible to purchase a large
H machine, spreading of solid waste into thinner layers and making more
MJ passes with a lighter machine may suffice. The optimum number of passes
depends on the moisture content and composition of the solid waste. Their
^1 exact relationships, as they affect density, have not, however, been
determined.
H Machines that operate on solid waste, especially during spreading
and compaction, are susceptible to overheating because of clogged radi-
ators, broken fuel and hydraulic lines, tire punctures, and damage in-
curred when waste becomes lodged in the tracks or between the wheels
and the machine body. The various accessories that are available to
Q| help alleviate these problems are discussed later in this chapter.
« Cover Material Handling. The excavating, hauling, spreading, and
compacting of cover material are similar to other earthmoving operations,
H such as highway construction. In landfill operations, however, rigorous
control of moisture content to achieve maximum soil density is not
^0 usually practiced, although it is desirable to wet a very dry soil
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somewhat to hold down dust and to improve compaction. The equipment
operator who spreads and compacts cover material should be capable of
grading it as specified to drain the site. Specific earthmoving require- H
ments vary according to the topographic and soil conditions present. _
Sand, gravel, and certain loamy clay and loamy silt soils can be excavated
with wheeled equipment, but tougher natural soils require tracked excavating H
machines. If the natural soil cover is thin, underlying formations com-
posed of weathered or partially decomposed bedrock may make suitable H
cover material, but they may have to be broken with a crawler equipped
with a rock ripper. Rippable materials include most uncemented shale,
thinly interbedded limestone and shale, poorly cemented siltstone, and
partially decomposed granitic rock types. These are, however, only gen-
eralizations, and a particular soil may be easier to excavate or more
difficult to work because soil properties may change significantly from
season to season. Glacial till can usually be excavated by heavy tracked
equipment if the compact clay has a moderate to high moisture content,
as in the spring and early summer. In the late summer and fall, when
less rain falls, glacial tills or clay soils of similar texture and
composition dehydrate and become very hard and difficult to excavate.
They must often be ripped first. Freezing weather may also require the
use of a rock ripper to remove the frost layer.
Support Functions. A sanitary landfill requires support equipment
to perform such tasks as road construction and maintenance, dust control, H
fire protection, and possibly providing assistance in unloading operations.
Road construction and maintenance must be provided so that the working ^R
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face can be reached in all types of weather. This often requires the
H adoption of a dust control program which, in turn, may call for the use
| of special equipment, such as a water wagon and sprinkler or a salt
spreader. Mobile firefighting equipment may be stationed on the site
or readily available nearby. Assistance in the unloading operation may
include emptying collection trucks equipped with a movable bulkhead and
IB pulling out vehicles that become stuck near the operating face during
M rainy weather. Unless there are many collection trucks requiring assist-
ance, the spreading and compacting machine can handle the situation.
Equipment Types and Characteristics
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A knowledge of the types and characteristics of earthmoving machines
is essential if the right selection is to be made, especially since most
machines can perform multiple functions.
H Crawler Machines. Crawler machines are of two types: dozer and
loader. Other common names for them are: bulldozer, crawler, crawler
dozer, track loader, front end loader, and bullclam; many trade names
are also used. They all have good flotation and traction capabilities,
because their self-laying tracks provide large ground contact areas.
The crawler is excellent for excavating work and moving over unstable
surfaces, but it can operate approximately only 8 mph, forward or reverse.
B The crawler dozer is excellent for grading and can be economically
mm used for dozing waste or earth over distances of up to 300 ft (Figure
19). It is usually fitted with a straight dozer blade for earthwork,
but at a sanitary landfill it should be equipped with a U-shaped blade
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Figure I-1.
Crawler dozer with landfill blade
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M that has been fitted with a top extension (trash or landfill blade) to
push more solid waste.
Unlike the crawler dozer, the crawler loader can lift materials
off the ground, but its bucket is not as wide, and it is not able, there-
H fore, to spread as much solid waste. The crawler loader is an excellent
M excavator and can carry soil as much as 300 ft. There are two types
of buckets usually used for sanitary landfill ing: the general purpose
H and the multiple purpose (Figures 20-21). The general-purpose bucket
is a scoop of one-piece construction. The multiple-purpose bucket, which
IB is also known as a bullclam or k in 1, is of two-piece construction,
_ is hinged at the top, and is hydraulically operated. It can thus clamp
onto such objects as tree trunks or telephone poles and lift and place
H them in the fill, or it can crush junked autos or washing machines. It
is also useful in spreading cover material. The general-purpose and
fjj multiple-purpose buckets come in many sizes. Matching a bucket to a
^ machine should be done with the advice of the machine manufacturer. A
^^ landfill blade similar to that used on dozers can also be fitted to loaders,
fl| Rubber-tired Machines. Both dozers and loaders are available with
rubber-tired wheels. They are generally faster than crawler machines
[I (maximum forward or reverse speed of about 29 mph) but do not excavate
_ as well. The plausible claim has been made that because the weight of
rubber-tired machines is transferred to the ground over a much smaller
II contact area, they provide better compaction, but significant differences
of in-place density have not been proven. Because their loads are concen-
11 trated more, rubber-tired machines have less flotation and traction than
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Figure ?.C.
Crawler Loader with General Purpose Bucket
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Figure 21.
Crawler Loader with Multiple Purpose Bucket
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crawler machines. Their higher speed, however, allows them to complete
more cycles or passes in the same amount of time than a crawler machine.
Rubber-tired machines perform satisfactorily on landfill sites if they
are equipped with steel guarded tires, called rock tires or landfill
tires. Rubber-tired machines can be economically operated at distances
of up to 600 ft.
The rubber-tired dozer is not commonly used at a sanitary landfill. H
Because of the rough and spongy surface formed by compacted solid waste H|
and the concentrated wheel loads, the rubber-tired dozer does not grade
as well as a crawler dozer. The flotation of the crawler dozer makes H
it much more suitable for grading operations. The rubber-tired dozer
should be equipped with a landfill or trash blade (Figure 22) similar
to that recommended for a track dozer.
The rubber-tired loader is usually equipped with a general-purpose
or multiple-purpose bucket (Figure 23). A particular asset of this
machine is the high speed and mobility of its operation. When it is
only needed part time at a sanitary landfill, it can be driven over public ^E
roads to perform other jobs. Because of its high operating speed, the
rubber-tired loader is especially suited for putting cover material into
haul trucks or carrying it economically over distances of up to 600 ft. H
Landfill Compactors. Several equipment manufacturers are marketing
landfill compactors equipped with large trash blades. In general, these H
machines are modifications of road compactors and log skidders. Rubber-
tired dozers and loaders have also been modified. The power train and
structure of landfill compactors are similar to those of rubber-tired
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FIGURE j?2.
Rubber tire dozer
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Ffgure 23.
Rubber-tire Loader
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machines, and their major asset is their steel wheels (Figure 2k). The-
wheels are either rubber tires sheathed in steel (Figure 25) or hollow
j steel cores; both types are studded with load concentrators.
Steel-wheeled machines probably impart greater crushing and com-
pactive effort than do rubber-tired or crawler machines. A study
comparing a ^7,000-lb steel-wheeled compactor, the same unit equipped
with rubber tires, and a 62,000-lb crawler dozer indicated that under
the same set of conditions, the in-place dry density of solid waste
compacted by the steel-wheeled compactor was 13 percent greater than
H that effected by the crawler dozer and the rubber-tired compactor.1
The landfill compactor is an excellent machine for spreading and
compacting on flat or level surfaces and operates fairly well on moderate
j slopes, but it lacks traction when operating on steep slopes or when
excavating. Its maximum achievable speed while spreading and compacting
H on a level surface is about 23 mph, forward and reverse. This makes
it faster than a crawler but slower than a rubber-tired machine. Since
^ landfill compactors operate at high speeds and produce good in-place
densities, they are best applied when they are used only for spreading
and compacting solid waste and cover material. When the cover material
J is a clay, it and some of the solid waste lodge between the load concen-
^- trators and must be continually removed by cleaner bars. The surface
of a soil layer compacted with a landfill compactor is usually covered
by pits or indentations formed by the load concentrators. Numerous passes
are needed to minimize the roughness of the surface.
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Figure 34.
Landfill Compactors
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r\
TAMPING
/\
TRIANGULAR
CLEAT
GEOMETRIC
FIGURE 25,
Steel wheel load concentrators
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Scrapers. Scrapers are available as self-propelled and towed models
having a wide range of capacities (Figure 26). This type of earthmoving
machine can haul cover material economically over relatively long Hj
distances (more than 1,000 ft for the self-propelled versions and
300 to 1,000 ft for towed models). Their prime function is to excavate,
haul, and spread cover material. Since they are heavy when loaded,
routing them over the fill area will help compact the solid waste.
Hauling capacities range from 2 to AO cu yd. II
Dragline. Large excavations can be made economically with a drag-
line. Its outstanding characteristic is its ability to excavate mod- H
erately hard soils and cast or throw them away from the excavation.
Because of this feature, it can also be used to spread cover material
over compacted solid waste. It is particularly useful in wetland opera- II
tions. The dragline is most commonly found at large landfills where
the trench method is used or where cover material is obtained from a
borrow pit. As a rule of thumb, the boom length should be two times ^_
the trench width. Buckets used at landfills usually range from 1 to
3 cu yd.
Special Purpose Equipment. Several pieces of earthmoving and road
construction equipment are put to limited use on landfills that dispose H
of less than 1,000 tons a day. Their purchase may not, therefore, be
warranted. When they are needed, they can be borrowed, leased, rented,
or the work can be performed under contract.
The road grader can be used to maintain dirt and gravel roads on
the site, to grade the intermediate and final cover, and to maintain
drainage channels surrounding the fill.
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.-' " *wL *«-''{'
V^JOT /%***,
*sS*' ' *' C ''r.
Figure 26. Scrapers
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Water is useful in controlling blowing litter at the working face
and control of dust from on-site roads. Water wagons range from con- Hi
verted tank trucks to highly specialized, heavy vehicles that are gen-
erally used in road construction operations. They can also be used at
the landfill to fight fires.
The road sweeper is a real asset at sites where mud is tracked onto
the public road system. Its periodic use will encourage local residents HI
to accept the landfill because roadways remain safe.
Accessor!es. The equipment used at landfills can be provided with
accessories that protect the machine and operator and increase the ef-
fectiveness and versatility of the machine (Table 8).
Engine screens and radiator-guards keep paper and wire from clogging H
radiator pores and causing the engine to overheat. A reversible fan
can also help alleviate this problem, because the direction of air flow
or vane pitch can be changed in less than 5 min. Under-chassis guards H
can be installed to protect the engine, and hydraulic lines and other
essential items of the machine should also be protected if they are sus- "
ceptible to damage (Figure 27).
The operator's comfort, safety, and efficiency can be increased
by providing roll bars, a canopy or cab, cab or helmet air conditioning,
and backup warning systems. A canopy is especially desirable for machines
that operate in a trench into which waste is dumped from above. Cabs
are particularly useful when the working area is very dusty or the operator
must work in very cold weather. Because rubber-tired machines and landfill
compactors operate at relatively high speeds, an audible backup warning H
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TABLE 8
RECOMMENDED AND OPTIONAL ACCESSORIES FOR LANDFILL EQUIPMENT
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Dozers Loaders
Accessory Crawler Wheel Track Wheel
Dozer blade 0" 0 - -
U-blade 0 0 - -
Landfill blade R1" R 0 0
Hydraulic controls R R R R
Rippers 0 0
Engine screens R R R R
Radiator guards-hinged R R R R
Cab or helmet
air conditioning 0 000
Ballast weights 0 0 R R
Multiple-purpose
bucket - - R R
General -purpose
bucket - - 0 0
Reversible fan R R R R
Steel-guarded tires - R - R
Lift-arm extensions - - 0 0
Cleaner bars - -
Roll bars R R R R
Backing warning system R R R R
*0-optional .
tR- recommended .
113
Landfill
compactor
0
0
R
R
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system should be provided to alert other equipment operators and personnel
in the immediate area. This system is also desirable on crawler machines,
^1 especially when two or more are operating in the same area.
Equipment versatility and effectiveness can be increased by use
of a number of accessories. A hydraulically operated ripper is needed
| when extensive excavation must be carried out in hard soils. It should
be mounted on a tracked machine to take advantage of its greater traction.
(Backrippers, hinged teeth attached to buckets or blades that dig into
the soil when the machine is reversing, are not as effective as hydraulic-
Bi ally operated rippers.) To give rubber-tired machines and landfill com-
pactors more traction, their wheels can be ballasted with a calcium
chloride solution or water, and steel or concrete counterweights can
be used on loaders and landfill compactors.
Different power trains can be used on many large machines. The
power shift and torque converter options are preferable to the dry clutch,
| direct-drive models because greater speed of operation and less strain
on the engine and operator are possible with them.
H Comparison of Characteristics. The ability of various machines
to perform the many functions that must be carried out at a sanitary
I landfill should be analysed with respect to the needs and conditions
of each site (Table 9). General recommendations regarding the best types
and sizes of machines to use at a specific landfill can be misleading.
^1 More exhaustive analysis is needed before the final equipment selection
is made.
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Size of Operation
Definition of functions and evaluation of equipment performance
must be matched with the size of the landfill to determine the type,
H number, and size of the machines needed. No one machine is capable of
performing all functions equally well. Neither can it be assumed that
Hi equipment effectively used at one site will be the most suitable else-
where. Unfortunately, production rates expressed in tons of solid waste
spread and compacted per hour are not readily available for comparison.
Guides that have been proposed by equipment manufacturers and others
should be considered only rough estimates of equipment needs for a par-
| ticular landfill (Table 10).
« Single-machine Sites. Particular difficulty is encountered when
selecting equipment for a site where only one machine will be used. It
must be capable of spreading and compacting both solid waste and cover
material, but it may also have to be used to excavate trenches or cover
material. In general, the most versatile machine for a small landfill
M is the tracked or rubber-tired loader. If the machine will not be used
full time, a wheeled loader is preferable because of its mobility. If
H the machine is to stay at the site full time and will not be required
to load cover material into trucks, a crawler dozer may be better.
| Regardless of the size of a single-machine operation, the depend-
_ ability of the machine should be high. Arrangements should be made in
advance to obtain a replacement if a breakdown occurs, because this de-
velopment is no excuse for unacceptable disposal. A replacement machine
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may be made available through the equipment dealer, a local contractor,
or a municipal public works department.
Small Sites. Municipalities disposing of less than 10 tons a day
may find the cost of owning a small dozer or loader too high. If ex-
cavation and stockpiling of cover material are done on contract, a farm
tractor equipped with a blade or bucket may be sufficient for spreading
the solid waste. The tractor will not, however, be able to produce much
compaction, even if the waste is spread in thin layers. The poor compaction
achieved means that a larger fill area will be needed. This requirement,
^1 together with the total cost of the contract work, should be compared
to the expense of owning and operating a small dozer or loader.
I Multiple-machine Operation. It is easier to select equipment for
a multiple-machine operation than it is for a one-machine operation.
Such specialized machines as scrapers and landfill compactors may then
be economical to use. If cover material has been stockpiled and more
than one machine is available, operations need not be interrupted when
IH an equipment breakdown occurs. As an added precaution, replacement
machines should be available through a lease, contract, or borrowing
arrangement.
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Costs
The equipment selected for a sanitary landfill must not only be
able to perform well under conditions present at the site, it must also
do so at the least total cost. Equipment costs, both capital and op-
crating, represent a significant portion of the expenses incurred in
operating a sanitary landfill.
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1
Capital Cost. Except for land, the cost of equipment may be the -mm
greatest portion of initial expenditures. The sanitary landfill equip-
ment market is very competitive, but rough approximations of costs have H
been developed (Table 11). A crawler machine weighing 29,000 Ib without
accessories costs about $29,000. With engine sidescreens, radiator guards, !
reversible fan, roll bar, and a multiple-purpose bucket, the same machine BM
costs approximately $32,000. A new dragline can cost between $75,000
and $110,000 depending on the length of its boom and cables, and the H
size of its bucket. In general, most landfill equipment used for exca-
vating, spreading, and compacting has a useful life of 5 years or 10,000 |§
operating hours. mm
The price of a used machine depends on its type, size, condition,
and number of recorded operating hours. Specific resale values are
available from auctioneers and manufacturers of earthmoving equipment.
The condition and remaining useful life of used equipment should be |
determined by an expert. mm
Operating and Maintenance Costs. Purchases of fuel, oil, tires,
lubricants, and filters and any expenses associated with routine main-
tenance are considered operating costs. Expenditures on fuel account
for approximately 90 percent of operating costs. The expense of operating ||
dozers, loaders, and landfill compactors varies according to type and mm
make; the manufacturer should, therefore, be consulted for specific
estimates. Generally speaking, direct operating costs are $3.00 per
hour. The skill of the equipment operator, the type of waste handled,
topography, and soil conditions also affect operating costs. |
120
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Maintenance costs, parts, and labor also vary widely but can be
approximated by spreading one-half the initial cost of the machine over
its anticipated useful life (10,000 hr). To make these costs more pre-
dictable, most equipment dealers offer lease agreements and maintenance
122
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contracts. Long downtimes usually associated with major repairs can
be reduced by taking advantage of programs offered by most equipment
dealers.
High operating costs are frequently associated with low initial H
costs of the equipment and vice versa. The purchaser should, therefore,
require that equipment bids include estimated operating costs. Hi
Actual operating and maintenance expenses should be determined during H
site operation by use of a cost accounting system.2 This information
can be used to identify areas where costs may be reduced; excessive fuel H
consumption, for example, may mean the machine needs adjustment or that -
operating procedures should be modified. Data from the cost accounting
system can be used to more accurately predict operating and maintenance
costs.
I
REFERENCES
1. Stone, R., and E. T. Conrad. Landfill compaction equipment ||
efficiency. Public Works, 100(5):111-113, May 1969.
2. Zausner, E. R. An accounting system for sanitary landfill opera- H
tions. Public Health Service Publication No. 2007. Washington,
U.S. Government Printing Office, 1969. 18 p.
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CHAPTER VI I I
COMPLETED SANITARY LANDFILL
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Reclaiming land by filling and raising the ground surface is one
H of the greatest benefits of sanitary landfill ing. The completed sanitary
landfill can be used for many purposes, but all of them must be planned
II before operations begin.
II Characteristics
The designer should know the proposed use of the completed sanitary
landfill before he begins to work. Unlike an earthfill, a sanitary land-
fill consists of cells containing a great variety of materials having
different physical, chemical, and biological properties. The decomposing
solid waste imparts characteristics to the fill that are peculiar to
H sanitary landfills. These characteristics require that the designer
plan for gas and water controls, cell configuration, cover material
IB specifications (as determined by the planned use), and the periodic
| maintenance needed at the completed sanitary landfill.
Decompos i t i on . Most of the materials in a sanitary landfill will
^1 decompose, but at varying rates. Food wastes decompose readily, are
moderately compactible, and form organic acids that aid decomposition.
Garden wastes are resilient and difficult to compact but generally
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decompose rapidly. Paper products and wood decay at a slower rate than
food wastes. Paper is easily compacted and may be pushed into voids, ^B
whereas lumber, tree branches, and stumps are difficult to compact and
hinder the compaction of adjacent wastes. Car bodies metal containers,
and household appliances can be compacted and will slowly rust in the H
fill with the help of organic acids produced by decomposing food wastes.
Glass and ceramics are usually easily compacted but do not degrade in
a landfill. Plastics and rubber are resilient and difficult to compact;
rubber decomposes very slowly, most plastics not at all. Leather and
textiles are slightly resilient but can be compacted; they decompose, H
but at a much slower rate than garden and food wastes. Rocks, dirt,
ashes, and construction rubble do not decompose and can be easily worked
and compacted.
Dens i ty . The density of solid waste in a landfill is quite variable.
One that is well constructed can have an in-place density as great as
1,500 Ib per cu yd, while that of poorly compacted solid waste may be
only 500. Generally, 800 to 1,000 Ib per cu yd can be achieved with
a moderate compactive effort. Soft and hard spots occur within the fill
as a result of different decomposition rates and compaction densities.
Density influences such other characteristics as settlement and bearing
capacity.
Settlement. A sanitary landfill will settle as a result of waste
decomposition, filtering of fines, superimposed loads, and its own weight. !
Bridging that occurs during construction produces voids. As the waste
decomposes, fine particles from the cover material and overlying solid
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waste often sift into these voids. The weight of the overhead waste
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and cover material helps consolidate the fill, and this development is
furthered when more cover material is added or a structure or roadway
is constructed on the fill.
The most significant cause of settlement is waste decomposition,
which is greatly influenced by the amount of water in the fill. A land-
fill will settle more slowly if only limited water is available to
l chemically and biologically decompose the waste. In Seattle, where
rainfall exceeds 30 in. per year, a 20-ft fill settled 4 ft in the first
H year after it was completed.1 In Los Angeles, where less than 15 in.
of rain falls per year, 3 years after a landfill had been completed a
H 75-ft high area had settled only 2.3 ft, and another section that had
jm been 46 ft high had settled a mere 1.3 ft.2
Settlement also depends on the types of wastes disposed of, the
volume of cover material used with respect to the-volume of wastes dis-
posed of, and the compaction achieved during construction. A fill
I composed only of construction and demolition debris will not settle as
Mj much as one that is constructed of residential solid wastes. A landfill
constructed of highly compacted waste will settle less than one that
H is poorly compacted. If two landfills contain the same types of wastes
and are constructed to the same height, but one has a waste-to-cover
1 volume ratio of 1:1 and the other a ratio of 4:1, the first will settle
less. Because of the many factors involved, a fill may settle as much
as 33 percent.3
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Settling can produce wide cracks in the cover material that expose _
the wastes to rats and flies, allow water to infiltrate, and permit gas ^
to escape. Differential settling may form depressions that permit water Hj
to pond and infiltrate the fill. Settling may also cause structures
on the landfill to sag and possibly collapse; the underground utility |
lines that serve these buildings or traverse the site may then shear.
Because every landfill settles, its surface should be periodically
inspected and soil should be added and graded when necessary.
Bearing Capacity. The bearing capacity of a completed sanitary
landfill is the measure of its ability in pounds per square foot to |
support foundations and keep them intact. Very little information is «
available on the subject, but a few investigators place the bearing
capacity of a completed landfill between 500 and 800 Ib per sq ft4;
higher values have, however, been noted.5 Since there is no definite
procedure for interpreting the results of solid waste bearing tests, |
any value obtained should be viewed with extreme caution. Almost without M
exception, the integrity and bearing capacity of soil cover depend on
the underlying solid waste. Most bearing strength tests of soil are H
conducted over a short periodseveral minutes for granular materials
to a maximum of 3 days for clay having a high moisture or air content. ||
During the test, the soil adjusts to its limits under the load imposed «
and conditions of confinement. Solid waste, on the other hand does not
follow this pattern of deformation but continues to alter its structure H
and composition over a long period of time. Natural soils, which are
not as heterogenous as solid waste, produce test values that fall within ||
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a predictable range. Moreover, repeated tests of the soil will produce
similar results--similar relationships have not been established for
« sol id waste.
Landfill Gases. Landfill gases continue to be produced after the
landfill is completed and can accumulate, in structures or soil, cause
explosions, and stunt or kill vegetation.6 Placement of a thick, moist,
| vegetative, final cover may act as a gas-tight lid that forces gases
« to migrate laterally from the landfill. If the site is converted into
a paved parking lot, this may also prevent the gases from venting into
^
the atmosphere. Design of gas controls should, therefore, conform with
the planned use of the completed fill.
I * Corrosion. The decomposing material in a landfill is very corrosive.
« Organic acids are produced from food, garden, and paper wastes, and some
weak acids are derived from ashes. Unprotected steel and galvanized
pipe used for utility lines, leachate drains, and building foundations
are subject to severe and rapid pitting. All structural materials sus-
1 ceptible to corrosion should be protected. Acids present in a sanitary
m landfill can deteriorate a concrete surface and thus expose the rein-
forcing steel; this could eventually cause the concrete to fail.
Uses
There are many ways in which a completed sanitary landfill can be
M used; it can, for example, be converted into a green area or be designed
for recreational, agricultural, or light construction purposes. The
landfill designer should evaluate each proposal from a technical and
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economic viewpoint. More suitable land is often available elsewhere
that would not require the expensive construction techniques required |
at a sanitary landfill. _
Green Area. The use of a completed sanitary landfill as a green
area is very common. No expensive structures are built, and a grassed
area is established for the pleasure of the community. Some maintenance
work is, however, required to keep the fill surface from being eroded |
by wind and water. The cover material should be graded to prevent water «
from ponding and infiltrating the fill. Gas and water monitoring stations,
installed during construction, should be periodically sampled until the
landfill stabilizes. Gas and water controls and drains also require
periodic inspection and maintenance. |
If the final cover material is thin, only shallow-rooted grass, »
flowers, and shrubs should be planted on the landfill surface. The de-
composing solid waste may be toxic to plants whose roots penetrate through H
the bottom of the final cover. An accumulation of landfill gas in the
root 2one may interfere with the normal metabolism of plants. This can |
be avoided by selecting a cover material having a low water-holding
capacity, but this type of soil provides poor support for vegetation.
On the other hand, a moist soil does not allow decomposition gas to disperse H
and consequently gas venting must be considered.
The most commonly used vegetation is grass. Most pasture and hay ||
grasses are shallow-rooted and can be used on a landfill having only «
2 ft of final cover, but alfalfa and clover need more than this. The
soil used for final cover influences the choice of vegetation. Some
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grasses, such as tall meadow oat grass, thrive well on light sand or
gravelly soils, while others, such as timothy grass, do better in such
H heavier soils as clays and loams.
Climate also influences the selection of grasses. Bermuda is a
I good soil binder and thrives in southern States. Perennial rye does
H best where the climate is cool and moist and winter is mild; it roofs
rapidly but dies off in two to three years if shaded. Redtop and bent
grass thrive almost anywhere except in drier areas and the extreme south.
The selection of the grass or mixture of grasses depends, therefore,
H on climate, depth of the root system, and soil used for cover material."
mm Mowing and irrigating requirements should also be considered. In gen-
eral, it is not advisable to irrigate the landfill surface, because the
^1 water may infiltrate and leach the fill.
Agriculture. A completed sanitary landfill can be made productive
B by turning it into pasture or crop land. Many of-the grasses mentioned
mm above are suitable for hay production. Corn and wheat usually have 4-
ft roots, but the latter occasionally has longer ones. The depth of
H the final cover must, therefore, be increased accordingly.
If cultivated crops are used, the final cover should be thick enough
| that roots or cultivating do not disturb its bottom foot. If the land-
mmi fill is to be cultivated, a 1-to 2-ft layer of relatively impermeable
soil, such as clay, may be placed on top of the solid waste and an
H additional layer of agricultural soil placed above to prevent the clay
from drying out. Excessive moisture will also be prevented from entering
* Information on the grasses mainly used in a landfill area is avail-
able from county agricultural agents and the U.S. Soil Conservation Service.
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the fill. Such a scheme of final cover placement must also provide for
gas venting via gravel trenches or pipes.
Construct ion. A foundations engineering expert should be consulted |B
if plans call for structures to be built on or near a completed sanitary
landfill. This is necessary because of the many unique factors
involved--gas movement, corrosion, bearing capacity, and settlement.
The cost of designing, constructing, and maintaining buildings is con- Bi
siderably higher than it is for those erected on a wel1-compacted earth
fill or on undisturbed soil. The most problem-free technique is to
preplan the use of islands to avoid settlement, corrosion, and bearing-
capacity problems. Ideally, the islands should be undisturbed soils
that are bypassed during excavating and landfill ing operations. Settle-
ment would then be governed by the normal properties of the undisturbed
soil. Alternatively, truck loads of rocks, dirt, and rubble could be
laid down and compacted during construction of the landfill at places
where the proposed structure woul-d be built.
The decomposing landfilled waste can be excavated and replaced with HI
compacted rock or soil fill, but this method is very expensive and could mm
prove hazardous to the construction workers. The decomposing waste emits
a very putrid smell, and hydrogen sulfide, a toxic gas, may be present H
with methane, an explosive gas. These two gases should be monitored
throughout the excavating operation. Gas masks may have to be provided mm
for the workmen, and no open flames should be permitted. mm
Piles can also be used to support buildings when the piles are
driven completely through the refuse to firm soil or rock. Some of the
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piles should be battered (angled) to resist lateral movement that may
occur in the fill. Another factor to consider is the load imposed on
the piles by solid wastes settling around them. The standard field
penetration resistance test is used to determine the strength of the
^1 earth material in which the piles are to be founded. During this test,
_ penetration will be resisted by the solid waste, but as the refuse
^ decomposes and settling occurs, it may no longer resist and will more
H likely create a downward force on the pile. There are no data for
established procedures for predicting this change in force.
H Several peculiar problems arise when piles are used to support a
structure over a landfill. The decomposing waste is very corrosive,
so the piles must be protected with corrosion-resistant coatings. It
may be very difficult to drive the piles through the waste if large
bulky items, such as junked cars and broken concrete, are in the fill
where the structure is to be located. The fill underlying a pile-
supported structure may settle, and voids or air spaces may develop
between the landfill surface and the bottom of the structure. Landfill
gases could accumulate in these voids and create an explosion hazard.
Light, one-story buildings are sometimes constructed on the land-
fill surface. The bearing capacity of the landfill should be determined
by field investigation in order to design continuous foundations.
^B Foundations should be reinforced to bridge any gaps that may occur because
of differential settling in the fill. Continuous floor slabs reinforced
as mats can be used, and the structure should be designed to accommodate
H settlement. Doors, windows, and partitions should be able to adapt to
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slight differential movement between them and the structural framing.
Roads, parking lots, sidewalks, and other paved areas should be con-
structed of a flexible and easily repairable material, such as gravel H
or asphaltic concrete.
Consolidating the landfill to improve its bearing capacity and 10
reduce settlement by surcharging it with a heavy layer of soil does not M
directly influence the decomposition rate. If the surcharge load is
removed and the structure is built before the waste has stabilized, H
settlement will still be a problem, and the bearing capacity may not
be as great as expected.
None of the methods for supporting a structure over a landfill are mm
problem-free. A common difficulty is keeping landfill gases from accumu-
lating in the structure. Even buildings erected on undisturbed islands H
of soil must be specially designed to prevent this from developing. A
layer of sand can be laid over the proposed structural area and then
be covered by two or more layers of polyvinyl chloride sheeting. An mm
additional layer of sand can then be enplaced. If the bottom layer of
sand is not saturated, it will act as a gas-permeable vent, and the ^1
sheeting will prevent the gas from entering or collecting under the
structure. The top layer of sand protects the sheeting from being ||
punctured. Another approach is to place an impermeable membrane of jute mm*
and asphalt under all below-grade portions of the structure. A gravel
or sand layer must underlie the jute-asphalt membrane and be vented to ^B
the atmosphere. The most reliable method is to construct a ventilated
false basement to keep gas from accumulating. |
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Utility connections must be made gas proof if they enter a structure
below grade. If the building is surrounded by filled land, utility lines
H that traverse the fill must be flexible, and slack should be provided
so the lines can adjust to settlement. Flexible plastic conduits are
B more expensive than other materials but would probably work best, because
M they are elastic and resist corrosion. Gravity wastewater pipelines
may develop low points if the fill settles. Liquid wastes should be
pumped to the nearest sewer unless the grade from the structure to the
sewer prevents low points from forming. Shearing of improperly designed
| water and wastewater services caused by differential settlement can occur
where thev enter the structure or along the pipeline that traverses the
fill.
I Recreation. Completed landfills are often used as ski slopes,
toboggan runs, coasting hills, ball fields, golf courses, amphitheaters,
| playgrounds, and parks. Small, light buiIdings, -such as concession
M stands, sanitary facilities, and equipment storage sheds, are usually
required at recreational areas. These should also be constructed to
H keep settlement and gas problems at a minimum. Other problems encountered
are ponding, cracking, and erosion of cover material. Periodic maintenance
B includes regrading, reseeding, and replenishing the cover material.
I Registration
H The completed landfill should be inspected by the governmental agency
responsible for ensuring its proper operation. Following final acceptance
B of the site, a detailed description, including a plat, should be recorded
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with the proper authority in the county where the site is located. This
provides future owners or users with adequate information regarding the
previous use of the site. The description should, therefore, include J|
type and general location of wastes, number and type of lifts, and «
details about the original terrain.
REFERENCES
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I
1. Dunn, W. L. Settlement and temperature of a covered refuse dump. H
Trend in Engineering (University of Washington), 9(0 :19-21,
Jan. 1957.
2. County of Los Angeles, Department of County Engineer and Engineering-
Science, Inc. Development of construction and use criteria for
sanitary landfills; an interim report. Cincinnati, U.S. Department
of Health, Education, and Welfare, 1969. [267 p.] |j
3. Refuse volume reduction in a sanitary landfill. Journal of the
Sanitary Engineering Division, Proc. ASCE, 85(SA6):37~50, Nov. 1959. I
4. Sowers, G. F. Foundation problems in sanitary landfills. Journal
of the Sanitary Engineering Division, Proc. ASCE, 94(SA1):103-116,
Feb. 1968.
5. Eliassen, R. Load-bearing characteristics of landfills. Engi-
neering News-Record, 129(11);103-105, Sept. 10, 1942. |
6. How to use your completed landfills. American City, 80(8):91~94, «
Aug. 1965. |
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"" CHAPTER IX
MANAGEMENT
The size and scale of operations carried out at a sanitary landfill
and the area served will influence the mechanics of management. The
H purpose and goal of solid waste managers should be to consolidate and
coordinate all the resources necessary to dispose of solid wastes in
" the most sanitary and efficient manner possib.le.
H Administrative Agency
H The responsibility for operating a sanitary landfill is normally
determined by the community administrative structure involved, and it
i must do so in the light of its own circumstances.
Municipal Operations. In most municipal operations, administrative
responsibility is assigned to the department of public works, one of
H whose divisions manages the solid waste program. As the scope of this
division's activities increases, it is desirable to subdivide the division
H into functional sections. Regardless of organizational structure, col-
lection and disposal plans and operations must be coordinated to achieve
satisfactory and economical solid waste management.
H Special Districts. Many States have enabling legislation that
permits the formation of special-purpose districts, which can include
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solid waste disposal districts. These districts are advantageous in HI
that they can serve many political jurisdictions and may have provisions
for levying special taxes. Before any special district is considered, H
the State laws applicable to them should be investigated. ^m
County Operations. A sanitary landfill administered by a county
may have advantages over a municipal operation. A county operation could
serve a number of incorporated and unincorporated areas using existing
governmental apparatus, and it might allow comprehensive planning for H
a larger geographic area. Other advantages are economy of scale and
greater availability of land. HI
Private Operations. Many sanitary landfills are operated success-
fully by private industry under a contract, franchise, or permit arrange-
ment. In contract operations, the municipality contracts with the
operator to dispose of its solid waste for a fixed charge per ton or
load. The municipality usually guarantees that the contractor will re- HI
ceive a certain minimum amount of money. Franchises usually grant the
operator permission to dispose of wastes from specified areas and charge
regulated fees. Permits allow the operator to accept wastes for disposal
without regard to source.
Private operations may be beneficial to municipalities that have HI
limited funds, but the community must not shirk its responsibility for
proper solid waste disposal. Of the three methods, contract operations
generally give the municipality the best guarantee that solid wastes HI
will be disposed of properly because standards can be written into the
contract.1 Franchises usually provide the next best control of operation. HI
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Administrative Functions
An administrative agency is responsible for proper solid waste
H disposal, including planning, designing, financing, cost accounting,
« operating, recruiting and training, informing the public, and establishing
minimum disposal standards.
Finance. Sanitary landfill capital costs include land, equipment,
and site improvements. Operating costs include salaries, utilities,
| fuel, and equipment maintenance. Equipment and maintenance costs were
^_ discussed in Chapter VII.
^^ There are several sources of funds to meet capital and operating
H costs." The general fund, derived from taxes, normally cannot provide
enough money to meet capital costs but is often used to pay for operating
| expenses. There are advantages to using the general fund for this purpose.
M The administrative procedures and extra cost of billing and collecting
are eliminated. Since all the taxpayers help pay for the sanitary land-
fill, they are more likely to use the sanitary landfill rather than an
open dump.
B Using general funds for landfill operations does, however, have
disadvantages. Cost accounting and other administrative procedures may
be so relaxed disposal costs are difficult or impossible to determine,
and users may have to be monitored. It may also be extremely difficult
for solid waste management operations to get money from the general fund
because of the low priority often assigned to them.
"Additional information is available from Solid Waste Management:
Financing, one of a series of guides developed by the National Association
of Counties Research Foundation.
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Genera] obligation borrowing is a common method of financing the
capital costs of a sanitary landfill. This type of bond generally carries
a low interest rate but is easily marketed because it is secured by the
pledge of real estate taxes and because all of the real estate within
the taxing district serves as security for the borrowed funds. State
statutes usually limit the amount of debt a community can incur. If
the debt is already substantial, this method may not be available. In
some cases, general obligation bonds are retired with revenues generated
by the landfill operation; this minimizes the ad valorem taxes necessary
for bond retirement. H
Revenue bonds differ from general obligation bonds in that they
are secured only by the ability of the project to earn enough to pay
the interest and retire the bonds. In this case, fees must be charged
to landfill users in amounts necessary to cover all capital and operating
expenses. It is necessary to set the fees high enough to accumulate H
a surplus over and above debt service needs in order to make the bonds mm
attractive to prospective purchasers. This method of financing requires
that the administering agency follow good cost accounting procedures, H
and it allows the agency to be the sole beneficiary of cost saving pro-
cedures. In addition, the producer of solid waste is forced to pay the H
true cost of its disposal. mm
User fees are primarily a source of operating revenue, but a munici-
pality might also employ them to generate funds for future capital expend!-
tures. The fees can be adjusted to cover not only the operating and
capital costs of present landfills but also to provide a surplus for
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acquiring land and equipment. Fees do not provide the capital outlay
^^ needed to start a sanitary landfill.
Although fees necessitate more work and expense because of the weigh-
ing, billing, and collecting involved, these requirements provide an
insight into the management and operation of the landfill. Commercial
haulers are usually billed on a per ton basis. Since the individual
_
" loads from homes are small, the users are charged on a per load basis
H to reduce weighing and bookkeeping. Because fee operations require that
collection vehicles be recorded at the gate, this provides an additional
11 control over wastes received at the landfill.
_ Operational Cost Control. A primary duty of administration is to
monitor and control the cost of operation. Cost accounting isolates
H the detailed expenses of ownership and operation and permits comparison
of costs against revenues. The important costs of operation include:
wages and salaries, maintenance of and fuel for equipment, utilities,
depreciation and interest on buildings and equipment, and overhead. Basic
«
data for cost accounting include the amount of waste disposed of at the
H fill, either by the ton or cubic yard. A cost accounting system recom-
mended for use at a sanitary landfill has been developed by the Solid
|| Waste Management Office.2
Performance Evaluation. In most cases, there is a control agency
at the State or local level that determines if the operation is being
conducted in a manner that safeguards against environmental pollution.
To ensure a sanitary operation, the administrative agency should conduct
its own performance evaluation. This should be done at the administrative,
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not the operating or supervisory level, and its requirements should be
at Veast as stringent as those of the higher control agency. While op-
erating and supervisory personnel should know that these inspections H
will occur at specified frequencies, they should not know the exact
day. This will help ensure a more representative inspection. |
Personnel. To secure and retain competent employees, the admini-
stration must have a systematic personnel management plan. First a job
description should be prepared for each position at the sanitary landfill.
A typical list of positions for a large operation might include: (1)
administrative tasks-- (management, accounting, billing, engineering, H
typing, filing); (2) operating tasks (weighing, operating equipment--
spreading, compacting, excavating, hauling, road maintenance, dust control--
maintaining equipment;^ traffic control, vector control, litter control,
si te securi ty).
Once the job areas are defined, management must determine how many
employees are needed; there may be some overlapping responsibilities.
For instance, a small sanitary landfill may need only one operator to
handle all its equipment. As the size of the operation increases, a H
division of labor will become necessary for sustained efficiency.
Governmental operations normally will have a civil service system H
that defines hiring and career-advancement procedures. In this case,
management's responsibility is to write good job descriptions and inter-
"Depending on the scale of operation, these tasks may be performed
on or off s i te.
view applicants. A potential employee should understand the job fully
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_ before he is hired. If he is expected to perform other duties during
^^ emergencies, he should be fully apprised of this fact. Management must
evaluate the ability of potential employees to comprehend and perform
their tasks before they are hired.
m Private operators may have more latitude in their employment prac-
_ tices. They should also interview and evaluate applicants as to interest
in the job, ability to do the work, and potential for increased responsi-
bi 1 ity.
Once an employee is hired, management must see that he is trained
|| properly. Such training should emphasize the overall operation of the
« landfill, safety, and emergency procedures. Employees responsible for
more critical and complex tasks are given more intensive training. Employees
should thoroughly understand work rules as well as procedures for handing
out reprimands and submitting grievances.
I Wages must be comparable with similar employment elsewhere. Larger
operations may increase employee satisfaction by providing lunch room
and locker facilities at the site. It is desirable to have on-the-job
training, insurance plans, pension plans, uniforms, paid holidays and
vacation, and sick leave programs.
I Publ ?c Rel at ions . Public relations is one of the manager's most
« important administrative functions. Solid waste disposal sites represent
an extremely emotional issue, particularly to those who live in the
H vicinity of a proposed site. Many sites are acceptable from an environ-
mental control aspect but are vigorously opposed by citizens who associate
| them with old-fashion open or burning dumps. Convincing the public of
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the advantages of a sanitary landfill is a tedious process but can be
accomplished by explanation and education. The program should begin
early in the long-range planning stages and continue after operations
begin. Public information should stress that at a sanitary landfill
the waste is covered daily, access is restricted, insects and rodents H
are controlled, and open burning is prohibited. Examples of properly «
operated sanitary landfills that have been accepted near residential
areas should be pointed out. Benefits to be derived by using the com- H
pleted site as a park or playground, for example, should be emphasized.
The media available to the solid waste manager are not limited to radio, B
television, billboards, and newspapers, but include collection vehicles,
collectors, disposal facilities, and billing receipts. Help provided
by community organizations can do much to increase public support. Ex- H
tensive "stumping" by elected and appointed officials in support of
a proposed solid waste disposal system is invaluable if the speakers
are knowledgeable and have sufficient aids to help them, such as slides,
films, and pamphlets.*
The single most important factor for winning public support of a H
solid waste disposal system is an elected or appointed official who firmly
believes that it is acceptable and needed. A person willing to accept |
the challenge of developing short- and long-range plans and to see that
they are properly implemented is invaluable. Once these plans are de-
veloped and implemented, the disposal system must be operated in a manner H
that upholds the high performance of which it is capable.
^Information pamphlets on the entire spectrum of solid waste manage-
ment is available from the Solid Waste Management Office and in a series
of guides issued by the National Association of Counties. II
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^_ A comprehensive solid waste management plan should be developed,
preferably on a regional basis. Detailed design and operating plans
^1 should cover a 10-year period and long-range, land-use planning should
be developed for 20 years. Appropriate locations for sanitary landfill
^| sites can then be identified, based on the needs of the area to be served.
_ These sites can be zoned for waste disposal or other usage that will
discourage development of a residential area. The regional approach
to planning and implementation is especially desirable because it often
is more economically feasible for all concerned. Land suitable for sani-
B tary landfill ing is usually scarce or nonexistent within the jurisdiction
of a large city. Smaller communities nearby may be able to provide the
land and thus be able to dispose of their own solid wastes in an accept-
H able manner.
A key aspect of public relations is the procedure for handling
|| citizen complaints. Deficiencies in operating methods or employee courtesy
_ should be investigated and acted on promptly. If this practice is followed,
citizens will be less hostile toward the operation, and employees will
H become more conscientious.
A sanitary landfill represents a positive and relatively inexpensive
|| step communities can take to provide a safe and attractive environment.
_ By proper design, operation, and management, sanitary solid waste disposal
can be provided.
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REFERENCES
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1. National Solid Wastes Management Association and Bureau of Solid ^
Waste Management. Sanitary landfill operation agreement and H
recommended standards for sanitary landfill design and construe-
tion. [Cincinnati], U.S. Department of Health, Education, and
Welfare, 1969. W p.
2. Zausner, E. R. An accounting system for sanitary landfill opera-
tions. Public Health Service Publication No. 2007. Washington,
U.S. Government Printing Office, 1969. 18 p.
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BIBLIOGRAPHY
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Committee on Sanitary Engineering Research. Survey of sanitary landfill
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Feb. 1958.
Winkler, T. E. Compaction, settlement of sanitary landfills. Refuse
Removal Journal, l(l2):8-9, 24-25, Dec. 1958.
148
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ACKNOWLEDGMENTS
The Solid Waste Management Office gratefully acknowledges the many
individuals who, over the past three years, assisted in developing the
outline and portions of the technical data contained in this publication
mm
and those who graciously reviewed the numerous drafts.
Members of the ad hoc panel chaired by Mr. Ralph Black included:
Donald Anderson, John Parkhurst, Joseph Salvato, John Vanderveld, Jr.,
|| Jean Vincenz, and William Warner. U.S. Public Health Service officers
mm John Wheeler and Charles Reid coordinated the first year efforts and
assembled the initial data; the latter also did much of the original
H work on finance and management,
Early drafts of this publication were reviewed by the American Society
j| of Civil Engineers; the American Public Works Association; the American
« Public Health Association; the Consulting Engineers Council; the National
Solid Wastes Management Association; the U.S. Department of Health,
j Education, and Welfare's Bureau of Community Environmental Management;
the Soil Conservation Service of the U.S. Department of Agriculture;
H the Bureau of Land Management and former Federal Water Quality Administra-
mm* tion of the Department of Interior; the Department of Defense; and
numerous State health agencies.
ya72-3-0014s
* US GOVERNMENT PRINTING OFFICE 1972 759-394/33
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