SW-72-1— 1
LANDFILL DECOMPOSITION GASES
AN ANNOTATED BIBLIOGRAPHY
SOLID WASTE RESEARCH LABORATORY
OFFICE OF RESEARCH AND MONITORING
NATIONAL ENVIRONMENTAL RESEARCH CENTER
CINCINNATI, OHIO
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LANDFILL DECOMPOSITION GASES
AN ANNOTATED BIBLIOGRAPHY
James A. Geyer
U.S. Environment Protection Agency
Office of Research and Monitoring
National Environmental Research Center, Cincinnati
June 1972
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ABSTRACT
This bibliography contains 48 articles on a variety of research
studies, case studies and observations on gases generated by the
decomposition of landfilled refuse. It includes annotations of arti-
cles on landfill gas generation and generation rates, gas composition,
gas movement rates and travel distances, and gas control techniques.
in
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FOREWORD
To find, through research, the means to protect, preserve, and
improve our environment, we need a focus that accents the inter-
play among the components of our physical environment — the air,
water, and land. The missions of the National Environmental
Research Centers — in Cincinnati, Research Triangle Park, N.C.,
and Corvallis Ore. — provide this focus. The research and monitor-
ing activities at these centers reflect multidisciplinary approaches to
environmental problems; they provide for the study of the effects
of environmental contamination on man and the ecological cycle
and the search for systems that prevent contamination and recover
valuable resources.
Man and his supporting envelope of air, water, and land must
be protected from the multiple adverse effects of pesticides, radia-
tion, noise, and other forms of pollution as well as poor management
of solid waste. These separate pollution problems can receive inter-
related solutions through the framework of our research programs —
programs directed to one goal — a clean livable environment.
This publication, published by the National Environmental
Research Center, Cincinnati, reports on work from this center.
Landfill Decomposition Gases: An Annotated Bibliography con-
tains reference information on landfill gas generation, gas movement,
and gas control. Municipalities, consultants, researchers, and others
concerned with gas production in sanitary landfills should find this
publication useful. Sanitary landfilling is, in most instances, one of
our most environmentally sound methods for disposing of the
continually mounting mass of solid wastes generated by the people
of our country.
ANDREW W. BREIDENBACH, Ph. D.
Director, National Environmental
Research Center, Cincinnati
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PREFACE
Sanitary landfilling is one of today's best available methods of
solid waste disposal. It is usually neat, safe, and inexpensive; we
often forget, however, that the decomposition of solid waste can
continue for many years. Decomposition of organic wastes will
yield gaseous products such as methane and carbon dioxide that
can have serious effects on the environment. Carbon dioxide will
dissolve in groundwater and thus contribute to increased hardness
and higher concentrations of pollutants. Methane is highly
flammable and, when trapped in a closed space, can create serious
explosions. There are recorded instances of both water-well
contamination by carbon dioxide intrusion and deaths by methane
explosions. Additional air pollution problems sometimes arise from
noxious decomposition odors. Controlling the environmental impact
of refuse decomposition gases is an essential part of proper sanitary
landfilling techniques.
This annotated bibliography attempts to document all known
publications on landfill gases for use in solving these environmental
problems. Most of these articles are nonscientific and several are
outdated. The older articles contain statements and concepts that
reflected landfill technology current with the time of the article.
Some of these statements and concepts are no longer valid because
of more recent findings from research studies and field monitoring.
The conclusions and findings reported here do not necessarily
represent the policy position of EPA.
Several annotations have been taken directly from two other
solid waste bibliographies: Solid Waste Management Practices:
An Annotated Bibliography and Permuted Title and Key-Word
Index, Oak Ridge National Laboratory, and Solid Waste Manage-
ment: Abstracts and Excerpts from the Literature, University of
California, Berkeley. These annotations are noted by (OR) and
(UC) respectively.
vn
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LANDFILL DECOMPOSITION GASES
AN ANNOTATED BIBLIOGRAPHY
AMERICAN PUBLIC WORKS ASSOCIATION, Municipal Refuse
Disposal, 2d ed., Chicago, Public Administration Service, p. 128-132,
134, 135 (1966).
Decomposition of landfills depends on many factors including
permeability of cover material, depth of burial and rainfall, mois-
ture content and putrescibility of the refuse, and degree of com-
paction. Refuse is composed primarily of carbohydrates, fats, and
proteins, which decompose to form humus and the gaseous end
products of carbon dioxide, methane, ammonia, and hydrogen
sulfide. Anaerobic decomposition occurs at elevated temperatures—
usually 100 to 120 F, but sometimes as high as 160 F.
Methane and carbon dioxide are the principal gases produced
during refuse degradation. Gas production has been noted to
decrease as moisture decreases. Hydrogen sulfide occurs when sea
water is allowed to enter a landfill.
Landfills may require many generations to completely decom-
pose. Studies in California estimate possible total decomposition
times of over 950 years. California also found that sizable carbon
dioxide concentrations will persist for many years and that landfill
gases will dissolve in groundwater.
A listing of the landfill gas control rules of the 1959 American
Public Works Congress is presented. The rules are used as guidelines
for safe building construction on completed sanitary landfills, and
they are based on the concepts that subsurface gases can be inter-
cepted and dissipated and that gases can be arrested by using subsur-
face enclosing envelopes of gastight construction.
ANDERSON, D. R., and J. P. CALLINAN, "Gas Generation and
Movement in Landfills," In Proceedings: National Industrial Solid
Wastes Management Conference, Houston (Mar. 1970).
A theoretical study of gas movement and gas generation was
applied to a hypothetical landfill. By comparing a sewage digester
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and the hypothetical landfill, it was theorized that a well-established
buffer system is important for optimal landfill gas production. The
aerobic processes that involve carbon dioxide production generate
moisture that helps establish a buffer system for anaerobic methane
production. Theoretically, a pound of refuse can produce 2.7 cubic
feet of carbon dioxide and 3.9 cubic feet of methane.
Gases flow through porous media by molecular effusion, molec-
ular diffusion, and convection. It was concluded that in landfills
the primary gas movement mechanism is convection and the basic
rate equation is Darcy's Law. The convection theory was then
applied to a two-dimensional landfill analogue (on electrical con-
ducting paper) predicting movement patterns.
BAUMAN, L. "Decomposition Creates Danger in Landfill," In 1964
Sanitation Industry Yearbook, p. 29.
In this short non-technical article, Bauman discusses methane
gas build-up in landfills that caused scares in Arlington, Mass., and
the Borough of Queens in New York City. After detecting methane
in and around buildings near the landfills, both cities constructed
gravel trenches to intercept and dissipate the gas.
BEVAN, R. E., Notes on the Science and Practice of the Controlled
Tipping of Refuse, London, The Institute of Public Cleansing,
p. 26-27 (1967).
The results of a refuse disposal field study in England are
reviewed in a brief section of the book. In practically every case
the reactions caused by bacterial activities on organic materials
result in the formation of a gas of some kind. The gases found in
the Wythenshawe study plots were hydrogen, methane, nitrogen,
carbon monoxide, oxygen, sulphuretted hydrogen, and carbon
dioxide.
Only two of the gases found, sulphuretted hydrogen and car-
bon monoxide, are definitely poisonous. Only small traces of sul-
phuretted hydrogen were detected in the plots and at no time in the
outside air. The carbon monoxide level seldom reached 1.0 per-
cent inside the test plots and was never at dangerous levels near
the surface or outside the plots.
Hydrogen, carbon monoxide, and methane might form explo-
sive mixtures when combined with air in certain proportions. Not at
any time, however, have any of these gases been present along with
oxygen in the correct proportions for the formation of an explo-
sive mixture; because the ignition temperature for any one of the
mixtures is very much higher than any recorded in the plots, no
danger is to be apprehended from the explosion hazard.
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The tip is nonodorous after sealing, unless specially pierced (as
when taking samples); in any case the odors, even within the tip, are
of short duration.
BISHOP, W. D., R. C. CARTER, and H. F. LUDWIG, "Gas Move-
ment in Landfilled Rubbish," Public Works, 96(ll):64-68 (Nov.
1965).
This is a report on one of the more scientific studies of landfill
gas movement. The objectives of the research study were to evaluate
the types and quantities of gases produced in landfills and the
movement of these gases horizontally and vertically. The test cell
contained 22,950 cubic yards (4,290 tons) of domestic rubbish,
which was placed in three 6- to 7-foot layers in an abandoned gravel
pit.
Gas sampling probes were positioned both inside and outside
the test cell. Carbon dioxide concentrations ranged from 60 to 70
percent, with one probe reaching a maximum of 89.4 percent. Over
80 percent of the gas probes had reached their respective maximum
carbon dioxide concentrations within 11 days after covering the test
cell. Hydrogen and methane concentrations reached maximums of
14 and 29.6 percent, respectively.
Carbon dioxide movement velocities through the landfill's
surrounding soils were estimated by using an approach basically the
same as that involved in determining the flow-through time in a
sedimentation tank. These "gross" velocities were calculated by
dividing the travel time (the difference between the date of initial
appearance of carbon dioxide and the date at which the carbon
dioxide concentration reached equilibrium) into the distance from
the refuse to the sample probe. The mean "gross" vertical and
horizontal velocities were 0.22 foot/day and 0.24 foot/day,
respectively.
The "net" quantity of carbon dioxide passing through a
certain area was calculated with the use of the following equation:
A r
n = V Y v Y -^— y W
^ X100 X100XW
where Q = net quantity of carbon dioxide (pounds/day)
V = "gross" velocity (feet/day)
Av= percent of void area
C = percent concentration of carbon dioxide
W = unit weight of carbon dioxide
The calculations established that the amount of carbon dioxide
entering the soil was: vertically, 18,700 pounds/year; horizontally,
3,300 pounds/year. This is equivalent to 5.1 pounds/year for each
ton of refuse in the test cell.
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BISHOP, W. D., R. C. CARTER, and H. F. LUDWIG, "Water
Pollution Hazards from Refuse-Produced Carbon Dioxide," Journal
of Water Pollution Control Federation, 38(3):328-329 (Mar. 1966).
This paper is one of the many reports on the Azusa landfill gas
movement studies conducted in southern California. The project
studied vertical and horizontal gas movement from a pilot scale
landfill placed in an abandoned gravel pit.
A noteworthy portion of this article discusses gas movement
theory and compares actual and theoretical results. Movement
downward results from molecular diffusion plus density differences,
whereas movement to the sides and upward to the atmosphere
results from diffusion alone. On a theoretical basis, one can calculate
the magnitude of diffusion into the soil and the atmosphere from
two different solutions of Pick's Law of Molecular Diffusion. One
can also calculate the flow due to density differences in accordance
with Darcy's Law, assuming that large pressure differences will not
occur and that the gases may be treated as incompressible fluids.
The results of both the theoretical and actual calculations for
carbon dioxide movement are as follows:
Observed Theoretical Density
Time Diffusion Diffusion Convection
Direction (days) (Ib/acre/yr) (Ib/acre/yr) (Ib/acre/yr)
Vertically downward
Horizontally
Upward through cover
*Acre of vertical interface.
550
550
718
809
24,400
22,700*
1.9 X 10s
3.0 X 10s
19,100
25,400*
9.2 X 10s
9.2 X 10s
12,800
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BRUNNER, D. R., andD. J.KELLER, Sanitary Landfill Design and
Operation, Rockville, Md., U. S. Environmental Protection Agency,
p. 56-61 (1971).
A general discussion of landfill gases — their properties and
hazards — is presented. Two types of gas control methods can be
used: permeable and impermeable. The permeable controls consist
of gravel trenches, pipe venting, and pumped exhaust wells. Clay
liners and synthetic membranes are impermeable controls. The
authors include excellent diagrams, explaining how landfill gas
control systems work.
BURCH, L. A., "Solid Waste Disposal and its Effect on Water
Quality," California Vector Views, 16(11):99-112 (Nov. 1969).
The following abstract is taken directly from the publication:
The disposal of solid wastes can cause impairment of ground or
surface water quality. The complex relationships between solid
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waste disposal and water quality are summarized in this general
discussion. Many types of municipal, industrial, and agricultural
solid wastes exist in forms which when disposed of improperly
may be sources of water pollutants. A relatively small number of
incidents of water quality impairment are on record, perhaps re-
sulting in complacency regarding this hazard. Some of the more
significant studies of this subject have been conducted in California
and are reviewed in this discussion. Solid wastes can be sources of
water pollutants by three processes: (1) physical removal, (2)
leaching, and (3) gas production, resulting in water quality im-
pairment in the form of floating debris, increased mineral content,
discharge of microorganisms, and potential release of toxic
substances.
This paper describes the possible effect of solid waste disposal
on ground water and surface water. Ground water may be ad-
versely affected by leaching soluble materials out of a landfill
resulting in the discharge of these pollutants into the ground
water. Carbon dioxide gas may also cause increased hardness and
corrosiveness of the ground water. Surface water can be impaired
by dumping solid wastes directly into the water or by the
physical erosion of portions of landfills located in floor plains
during flood conditions. Measures available for control and pre-
vention of water quality problems from solid waste disposal are
also briefly discussed. These include categorization of solid
wastes for their disposal in landfills qualified to accept them due
to the physical characteristics of the disposal site. Also discussed
are landfill construction and operation techniques and application
of water during the final use of the landfill. Research which is now
under way is envisioned to provide some of the answers needed to
preclude water quality impairment from solid waste disposal.
BURCHINAL, J. C., and H.A.WILSON, Sanitary Landfill Investi-
gation, Final Report, Research Grant No. SW-00040-01, 02, 03,
Department of Health, Education, and Welfare, unpublished (Aug.
1966).
The authors undertook, over a 25/2-year period, a laboratory
research study of the production of gas and volatile acids from
sanitary landfills with the use of steel cylinders filled with refuse.
The use of ground and unground refuse was compared by studying
the pattern of gas generation. Emphasis was placed on biochemical
actions occurring in sanitary landfills. Temperature, volatile solids,
and C/N ratios proved to be unsatisfactory parameters for defining
the course of decomposition. Analyses of gas and volatile acids
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produced as a result of microbial metabolism provided evidence as
to mechanisms involved in the process.
Some of the more significant results and conclusions included
in the paper are:
1. Hydrogen, oxygen, nitrogen, carbon dioxide, and methane
would be the major gases in a normally constructed sanitary
landfill. Trace amounts of hydrogen sulfide could be formed in
the first week, but the chance of its presence beyond the part
per million level in the first 2 years would be small. The landfill
would not release gaseous ammonia except under high pH
conditions.
2. Hydrogen was produced in great quantities during the first 3
weeks. The maximum content of 20.6 percent was produced
between the first and second week. It declined to about 1 per-
cent at the end of 1 month but was present at the 0.1 percent
level over the years investigated. The presence of molecular
hydrogen was indicative of the reducing system operated at an
oxidation-reduction potential well below that of the hydrogen
electrode and was also evidence of anaerobic conditions.
3. Two weeks after placement of refuse, carbon dioxide was
produced to a maximum of 85 percent. Following the maxi-
mum peak, the content of carbon dioxide rapidly reduced and
approached 40 percent at the end of 2 months. The rate of
change in carbon dioxide after the sixth month was small and
generally stayed in the level of 40 percent.
4. Trace amounts of methane were produced during the second
week. In one of the cylinders, it reached 2.7 percent at the end
of 2 months, 6 percent in the sixth month, 13 percent at the
end of 1 year, and 20 percent at the end of 2 years. Other
cylinders showed much lower methane contents. Low pH and
trace amounts of oxygen could inhibit methane bacteria.
Saturation of refuse with water would probably enhance
methane production.
5. Stratification of gases occurred within the cylinders. Contents
of carbon dioxide, methane, and hydrogen were higher in the
lower portion, whereas the content of nitrogen was higher in
the upper portion.
6. Composition of gas in landfills was related to compaction
densities of refuse, particularly in the early period when
production of carbon dioxide and hydrogen was high. With
the higher compaction density, there is less void space within
the refuse, but more organic materials available per unit volume
to produce gases.
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7. Results of both gas and volatile acids analyses indicated that
the most pronounced changes in organic materials occurred
within the first 60 days. Accumulation of intermediate
products indicated, however, that organic materials in landfills
were far from stabilized even at the end of 2 years.
CALIFORNIA DEPARTMENT OF WATER RESOURCES, Sanitary
Landfill Studies, Appendix A. Summary of Selected Previous
Investigations, Bulletin No. 147-5, Sacramento (1969).
The authors of this publication summarized the major landfill
research studies conducted in southern California. The following
abstract appeared in the publication:
Three principal techniques used for the disposal of refuse are
incineration, open dumps, and sanitary landfills, of which land-
fills are the most useful and effective. This report not only gives
information on landfills from investigations by the Department
of Water Resources, but also summarizes the work of other
investigators. / Decomposition of refuse in landfills results in the
formation of gases. If sufficient water is available, these gas
products may dissolve. Soluble organic and inorganic compounds
may also be dissolved, forming leachate. / Instances of gas and
leachate impairment of ground water are cited in this report. All
of which indicate the necessity for control measures. They show
that sanitary landfills should be designed as a system, with prime
consideration given to site selection, materials to be deposited,
construction and operation techniques, and use of the completed
fill. / The report describes a system for classifying the physical
characteristics of a site according to the degree of protection
afforded receiving waters and for determining what type refuse
could be disposed in each.
CALIFORNIA STATE WATER POLLUTION CONTROL BOARD,
Effects of Refuse Dumps on Ground Water Quality, Publication No.
24, Sacramento, p. 47-67 (1961).
Decomposition processes and rates are believed to be closely
connected with the circulation of air and decomposition gases
through refuse fill. Gas movement can occur by displacement when
there is a net production or uptake in the refuse and by convection
due to differences in gas density. Density variations may arise
when portions of the refuse atmosphere receive heat liberated in the
decomposition process and when the gas produced has an average
molecular weight different from that of air. However, the most
effective transfer mechanism is molecular diffusion; the diffusivity
of a porous medium is relatively independent of the particle size, so
gases may diffuse readily through some materials of low permea-
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bility. Therefore, in preventing carbon dioxide from moving into
the underground, methods that involve its removal to the atmosphere
by encouraging draft or ventilation may be more effective than
coatings to decrease permeability of the disposal pit surf aces. (UC)
The report includes discussion of the basic aerobic and anaero-
bic processes that generate landfill gases and the quantities of gas
that might be produced. A description of landfill gas properties and
a good explanation of gas movement by diffusion and convection
are also presented. The theories for generation and movement are
substantiated by known data wherever possible.
CALIFORNIA STATE WATER POLLUTION CONTROL BOARD,
Report on the Investigation of Leaching of a Sanitary Landfill,
Publication No. 10, Sacramento, p. 13, 53-56 (1954).
Limited gas study was conducted in conjunction with leaching
research at a Riverside landfill site. This section of the report in-
cludes information on sampling equipment and techniques and
tabulations of gas concentration data from new and old landfill
areas.
It was concluded that anaerobic conditions with production of
combustible gas will exist within a sanitary landfill in approximately
1 month following deposition of the fill.
Air in the fill is consumed by aerobic decomposition of the
refuse. The following are typical oxidation reactions for carbo-
hydrates and stearic acid:
C6 H12 06 + 6 02 - 6 C02 + 6 H2 O
C,8 H36 02 +2602 = 18C02 + 18H20
After the oxygen is used up, the anaerobic decomposition of the
waste results in an increased quantity of gas (methane and carbon
dioxide) which creates increased pressure and subsequent gas
diffusion:
C6 H12 06 = 3 C02 + 3 CH4
CIB H36 O2 +8H2O = 5CO2 + 13CH4
CALIFORNIA STATE WATER QUALITY CONTROL BOARD,
In-situ Investigation of Movements of Gases Produced from De-
composing Refuse, Publication No. 31, Sacramento (1965).
The authors have compiled in this technical report complete
information about all phases of a research project at Azusa, Calif.,
on the movement of refuse decomposition gases through a landfill.
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Because of concern about possible groundwater pollution from
use of abandoned gravel pits for disposal of solid wastes, this study
was undertaken to evaluate the movement of refuse decomposition
gases, both laterally and vertically, through a refuse fill and adjacent
strata. Carbon dioxide was the only decomposition gas found in
significant quantities in the adjacent and surrounding soil. About
18 times the quantity of carbon dioxide and about 24 times the
quantity of methane passed through the 1-foot silt cover into the
atmosphere as passed into the surrounding soil. If it is deemed
necessary to isolate carbon dioxide from groundwater, control
methods must be formulated.
The active "life" of the refuse fill was estimated on the basis
of the total carbon initially present in the refuse and on the past and
present rates at which carbon has passed out of the fill. On the
assumption that the calculated initial amount of carbon was
"available," the following projections were made:
Percent of CO2 Concentration in
Initial Carbon Gone Years Bottom Refuse Layer
50 57 12 percent
90 950 3 percent
CALIFORNIA STATE WATER QUALITY CONTROL BOARD,
In-situ Investigation of Movements of Gases Produced from De-
composing Refuse, Final Report, Publication No. 35, Sacramento
(1967).
Over 90 percent of the gas produced by refuse decomposition
in large landfills is carbon dioxide and methane. Both of these gases
were found in concentrations up to 40 percent at distances up to
400 feet away from the edge of the fill. An equal concentration of
carbon dioxide can be found in the soil under a landfill if the soil
is homogeneous and not impervious. Methane poses less of a
threat to groundwater quality because it is only slightly soluble in
water. Moreover, since it is lighter than air, it will tend to rise
through the landfill rather than diffuse into groundwater.
Refuse gases pose more of a hazard to groundwater than
leachates because gases are always produced, whereas the leachate
problem is one of external water passing through the refuse. Proper
location and maintenance of the fills help avoid leachate problems.
A workable and effective carbon dioxide gas barrier membrane was
developed. (Using such a membrane would increase the cost of
landfill operation by 10 percent or less.) Methane production in
pits constructed to test the effectiveness of an asphalt barrier was
not great enough to permit a conclusive determination of the
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effectiveness of this type of barrier. A more effective gas control
procedure would be one in which the gas is vented and burned. (UC)
This publication is one of the best and most comprehensive
reports on landfill gases.
CALLAHAN, G. P., and R. H. GURSKE (Bureau of Sanitation, City
of Los Angeles) "The Design and Installation of a Gas Migration
Control System for a Sanitary Landfill," presented at The First
Annual Symposium of the Los Angeles Forum on Solid Waste
Management, May 1971, in Pasadena, Calif.
Research on landfill gas control systems at two Los Angeles,
Calif., sanitary landfills is summarized in this technical report. The
two sites (Branford and Sheldon-Arleta) are constructed in old
gravel pits, and in both locations, gas generated from refuse de-
composition has migrated beyond the fill area. Extensive tests at
both landfills have resulted in the development of an effective
method to control gas migration.
After extensive gas movement was discovered, the Branford
site was equipped with a gas well test installation. Five wells, spaced
on 40-foot centers and gravel filled, were placed at various depths
and the withdrawal lines installed in each well were connected to a
header and ventilation blower. Several tests determined the efficiency
of the various wells at different air flow rates, blower cycle times,
and well combinations. It was found that gas migration may be
controlled with a well spacing of between 300 and 400 feet with a
withdrawal rate as low as 200 cfm per well.
At the Sheldon-Arleta landfill site, three 24-inch diameter
wells were drilled and a single withdrawal line installed in each well.
The wells were at various depths, gravel filled, and connected to a
main header leading to a withdrawal blower. Again, tests utilized
different flow rates, blower cycles, and well combinations. The con-
clusions from the Branford study were confirmed with respect to
well spacing and withdrawal rate required. It was also concluded
that the withdrawal rate is apparently a function of well spacing and
that well depth in the range tested is not a significant factor.
Based on the information obtained from the Branford and
Sheldon-Arleta tests, the city of Los Angeles has installed a $ 115,800
gas control system to protect houses and a high school at the
Sheldon-Arleta site. The system consists of 17 wells, 25 feet deep,
spaced on 150-foot centers, with a designed withdrawal rate of 200
cfm each. The 2-foot diameter ventilation wells were drilled in
natural soil and held a 6-inch diameter perforated PVC pipe packed
in gravel. The wells are connected to a vitrified clay pipe header
that runs three-fourths of a mile to a 15-horsepower fiberglass
blower. The blower feeds an induced draft vapor fume incinerator
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that uses natural gas as a supplementary fuel. The system will
completely protect the surrounding neighborhood and provide
excellent facilities for future gas migration research.
CARPENTER, L. V., and L. R. SETTER, "Some Notes on Sanitary
Landfills," American Journal of Public Health, 30(4):385-393
(Apr. 1940).
The article is a report on one of the first "scientific" in-
vestigations on sanitary landfills. The researchers used gas probes
at several different depths to obtain gas concentration data from
landfills in "dry" conditions and "wet" (located in water table)
conditions. The equipment and procedures used were very crude,
but this is the earliest known attempt to collect and identify gases
from landfilled refuse.
COE, J. J., "Effect of Solid Waste Disposal on Ground Water
Quality," Journal of the American Water Works Association,
62:776-783 (Dec. 1970).
Leachate and carbon dioxide from refuse decomposition have
been responsible for groundwater degradation in California. Carbon
dioxide can impair groundwater by affecting acidity, alkalinity, and
hardness.
The California State Department of Water Resources has
studied carbon dioxide impairment of groundwater at Azusa and
Monrovia (Mayflower Well), Calif. Some of the more important
findings from this article that includes detailed summaries of these
two studies are:
l.Gas production quantities vary directly with temperature,
moisture content, garbage content, and aeration. Dry refuse and
saturated refuse produce ,0.035 and 0.210 cubic foot of gasper
pound of refuse on a dry basis, respectively, as determined
experimentally. Gas movement rates were found in this study
to be 0.22 to 0.8 foot/day vertically, and 0.24 to 1.4 feet/day
horizontally in undisturbed alluvial soils.
2. Carbon dioxide effects on groundwater are increases in hard-
ness and bicarbonate. Depending on the pH after carbon
dioxide absorption, water may become corrosive.
3. Pollution does not necessarily occur at the same time a landfill
is constructed. Completed fills can exist for years before any
effects on groundwater are detected.
The author also describes California's landfill rating system.
Landfill sites can be modified—usually by construction of a physical
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barrier—to protect the groundwater. The physical barriers used are
clay layers, plastic membranes, and asphalt liners. Studies on asphalt
and polyethylene sheet indicate carbon dioxide concentrations are
reduced 75 percent and 50 to 60 percent, respectively. Future
studies will include development of a natural ventilation system.
DUNN, W. L., "Landfill Gas Burned for Odor Control," Civil
Engineering, 27(11):60-61 (Nov. 1957).
The author discusses an incident at a landfill at the University
of Washington grounds in which methane gas was ignited. An in-
expensive burner was made by welding a short piece of ^-inch wire
mesh screen onto one end of 1-inch diameter tubing. The screen was
then placed 6 to 12 inches into the refuse with earth compacted
around it. A low pressure flame retention gas burner was inserted
about 2 inches from the top of the tubing. To burn the refuse gas, a
tight earth seal had to be maintained.
DUNN, W. L., "Settlement and Temperature of a Covered Refuse
Dump," The Trend in Engineering, 9(1): 19-21 (Jan. 1957).
In this short report on observations made at the Union Bay
refuse disposal site in Seattle, Dunn presents several comments on
gas and odor problems. A very hot gas fire was discovered in a 20-
to 30-foot long settlement crack. There was no smoke, and the
surrounding soil was red hot. Gas bubbles were also seen where
water had accumulated on the fill surface. Later, a 1%-inch pipe
was driven into the landfill and used as a waste j*as burner. Gas
burners were then used for odor control at other locations.
DUNN, W. L., "Storm Drainage and Gas Burning at Refuse Disposal
Sites," Civil Engineering, 30(8): 68-69 (Aug. 1960).
On a refuse disposal site loaned by University of Washington to
city of Seattle, French drains about 20 feet wide, 10 feet deep, and
several hundred feet long were constructed to abduct storm waters
and collect gases. Controlled burning at specially constructed inlets
oxidized methane and destroyed foul odors. (OR)
This article is a non-technical report of the author's observa-
tions at the landfill site.
ELIASSEN, R., "Why You Should Avoid Housing Construction on
Refuse Landfills," Engineering News-Record, 138(18):90-94 (May
1, 1947).
An early attempt to control landfill gases and odors is
recorded.
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Erection of veterans' emergency housing units in New York
City called for the use of a 130-acre site that had been filled with
rubbish and garbage some 5 years earlier. Regrading the site and
opening trenches for utilities exposed decomposing garbage with its
resulting stench.
A commercial oxidizing agent sprayed on the exposed refuse
successfully controlled these odors. To cope with the problem of
combustible gas generation within the fill, all the houses were
elevated above the ground and an aluminum foil membrane was
secured under the wood flooring. On the basis of these experiences,
the conclusion is reached that landfills should not be used for
purposes requiring excavation. (OR)
ELIASSEN, R., F. N. O'HARA, and E. C. MONAHAN, "Sanitary
Landfill Gas Control," The American City, 72(12): 115-117 (Dec.
1957).
The town of Arlington, Mass., discovered explosive concentra-
tions of methane gas near an old landfill site that endangered
several homes and a business. The discovery was originally believed
to be a natural gas line leak, but the presence of high carbon dioxide
concentrations and no signs of ethane indicated the landfill as the
gas source.
A weekly sampling routine was initiated to monitor concentra-
tions and a long gravel trench was installed to intercept and vent the
gas. Before the trench was installed, explosive concentrations of gas
were consistently recorded 600 feet away from the landfill.
"Explosion and Fire Traced to Refuse Generated Gases," Refuse
RemovalJournal, 6(8):34 (Aug. 1963).
Methane, hydrogen, and ammonia are dangerous gases formed
by the bacterial decomposition of organic material. A recent report
or a study of the causes behind six cases of fire and explosion from
the U. S. Bureau of Mines Explosives Research Laboratory makes
this point clear.
An explosion that demolished a nearby house was traced to
gases generated by sewage dumped into an abandoned mine.
Gases bubbling through pools of water on a school construction
site were found to be flammable, and there was a vegetable decay
odor in the area. The investigators from the Bureau's explosives
research laboratory found that the building's foundations were
located directly over an old garbage dump.
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In another investigation, it was discovered that an inflammable
gas had been admitted to a house through the accidental connection
of a storm sewer to a sanitary disposal pipe line. (OR)
FIRST, M. W., F. J. VILES, Jr., and S. LEVIN, "Control of Toxic
and Explosive Hazards in Buildings Erected on Landfills," Public
Health Reports, 81(5):419-428 (May 1966).
The actual field application of landfill gas control tech-
nology on a construction project is discussed in this article. The
principal hazard involved in construction on refuse-filled land
arises from the anaerobic production of combustible gases. Gastight
construction over landfills is difficult if not impossible to achieve
because of the gas pressure resulting from biological gas production.
During investigations of gas levels in a housing development
constructed on sanitary landfills, the concentration of methane was
at an unsafe level in a high proportion of the buildings. A concrete
slab laid on top of the fill did not prevent gases from getting into
the buildings. Several sealants (Flintkote C-13-A asphalt emulsion;
Flintkote No. 70 asphalt emulsion; sodium silicate; water) proved
to be inadequate for the purpose.
Results of periodic sampling over several years in the sub-
basement spaces of a number of buildings indicated that organic
fill located around and under the heated buildings became complete-
ly degraded in approximately 5 years, releasing methane at a
proportionately rapid rate. A situation such as this can constitute a
serious explosion hazard unless suitable methods of aeration and
ventilation are employed. Continuous mechanical aeration at a rate
of one or two air changes per hour adequately reduced the methane
concentration. (UC)
FLOWER, F. B., and L. A. MILLER, "Report of Investigation of
Vegetation Kills Adjacent to Landfill," New Brunswick, N. J.,
Cooperative Extension Service, College of Agriculture and Environ-
mental Science, Rutgers University (1969).
Flower and Miller investigated the death of several trees,
bushes, and shrubs on land adjacent to a landfill. Most of this
vegetation grew within 15 feet of the landfill. The soil was sandy
and at the time of the investigation had 2 to 3 inches of frost. It was
believed that the frost may have encouraged the gas movement.
The following are the authors' summary and conclusions:
Excessive amounts of carbon dioxide and combustible gases
were found in the soil of the property. The concentrations
decreased as distance from the landfill increased.
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It appears from the "gross and quick" tests conducted by
Flower and Miller that the vegetation deaths at the rear of the
property adjacent to the Cherry Hill sanitary landfill could be due
to the displacement of oxygen from the root system of the
vegetation by gases of decomposition traveling laterally from the
landfill. Corrective measures should be taken which will prevent
the gases from traveling beneath the property in excessive
quantities. This might be accomplished by placing a gas flow
barrier in the ground at the rear of the property or by relieving
the landfill gas pressure through well pipes.
FUNGAROLI, A. A., Pollution of Subsurface Water by Sanitary
Landfills, Final Report, Research Grant No. R01-UI00516, Depart-
ment of Health, Education, and Welfare, p. 28, 47-51, unpublished
(1970).
In this landfill study of a laboratory-scale fill in a lysimeter
and a field-scale fill, gas-concentration histories were kept for over
2 years. The report describes the sampling probes and procedures
and discusses the gas analysis employed.
"A Gas Control and Monitoring System," Public Works, 101 (12): 39
(Dec. 1970).
The following is the entire article as it appeared in the
periodical:
Engineering Sciences is serving as a special consultant to the firm
of McKee, Berger, Mansueto, Inc (MBM), project managers for
construction work under way for the University of Massachusetts
at Boston. C. Ronald Rabin is the MBM Project Manager. The
construction is taking place on a completed dump site and
significant quantities of methane gas and traces of hydrogen sul-
fide have been identified and located, and ES is developing a gas
control and monitoring system and the design of facilities to
protect against the movement and dangerous concentration of
gases.
Following identification of the gases, probes and monitoring
with gas detection equipment were used to develop gas concentra-
tion contours, and a gas control system (consisting of three
principal devices) is being designed to permit safe building
occupancies. The primary device is a gas evacuation network
composed of perforated piping, collectors, and variable speed
pumps which will remove gases from under the buildings. A
barrier mat will be installed before the floor slab is poured and
all utility entries will be sealed to prevent any gases from entering
15
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the buildings. A safeguard monitoring system will also be install-
ed to detect the presence and concentration of methane and to
activate the gas evacuation pumps. The monitoring system will
also provide a total check on the system performance.
"Gas Fire in Sewer Manhole Traced to Sanitary Fill Operation,"
Engineering News-Record, 139(26): 51 (Dec. 25, 1947).
Because of bad weather, the city of Knoxville, Tenn., sealed
off its 3-year-old landfill with clay earth. Within 2 weeks, blue
flames and intense heat poured out of a sewer manhole located in
the fill. Methane gas from the decomposition in the landfill had
seeped through the sides of the manhole and ignited; this caused the
manhole to act like a giant Bunsen burner.
The article is a short description of the incident.
"Gas Fires in a Sanitary Fill," Engineering News-Record, 140(2): 86-
87 (Jan. 8, 1948).
San Francisco's landfill experienced several gas fires caused by
spontaneous combustion of venting gases. The fill, located in a
tidal area, was 50 to 60 feet deep and was believed to have decom-
position temperatures of 160 to 180 F. The gas fire flames were
notably low temperature and colorless.
A crude sampling port was dug 5 feet deep into a 12-year-old
portion of the fill. Because the sample port was not airtight, the
observers did not know if air was present inside the fill. Assuming
that all the air in the sample leaked in from the atmosphere, the gas
analysis was 25 percent carbon dioxide, 60 percent methane, 9
percent hydrogen, and 6 percent nitrogen.
It was believed that an anaerobic condition existed because of
the limited amount of degradation on 12- to 15-year-old refuse
samples taken from the fill.
"How to Use Your Completed Landfills," The American City,
80(8):91-94 (Aug. 1965).
A survey of counties that used sanitary landfill for their solid
waste disposal showed that 48 percent of the 208 that responded
to the survey did not have any structures on the completed landfill
sites, 21 percent had built on one or more sites, and 31 percent had
not as yet completed any landfills. Settlement, gas production, or
both have adversely affected many of the structures constructed on
completed sanitary landfills.
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The article describes responses from many counties throughout
the Nation. In general, the consensus was that buildings must have
adequate protection from settling and gas seepage. One city initiated
the following requirements: a monolithic, self-supporting founda-
tion slab, keyed and sealed foundation walls, a plastic seal under
the interior floor, and a 24-inch-wide rock-filled trench around the
foundation to collect gas.
Golf courses, playgrounds, parks, and picnic areas are suitable
uses for completed landfills, although gases produced by the decom-
posing refuse often make it difficult for grass and other flora to
grow.
"Is There Danger Where There Is Decomposition?" The Surveyor,
104:817 (Dec. 28,1945).
The author regards carbon dioxide as a poisonous gas and cites
three suffocation accidents in which eight men died. Because it is
heavier than air, carbon dioxide will collect in low areas such as
sumps and manholes; since it is generated by waste decomposition,
it is a hazard around refuse fills, sewage digesters, and septic tanks.
LIN, Y. H. Acid and Gas Production from Sanitary Landfills,
dissertation, West Virginia University, p. 36-44, unpublished (1966).
A laboratory research study was conducted on three simulated
landfills placed in 8-foot by 2-foot-diameter steel cylinders. Gas
concentration histories were recorded for hydrogen, oxygen, nitro-
gen, methane, carbon dioxide, ammonia, and hydrogen sulfide
produced in the cylinders.
The report includes gas concentration plots for the first 2
months of the study and a discussion of the microorganisms involved
with refuse decomposition. (This dissertation was done in con-
junction with a larger research study at West Virginia University.
For additional information, see the annotation on Burchinal, J.C.,
and H.A. Wilson.)
MAC FARLANE, I. C., "Gas Explosion Hazards in Sanitary Land-
fills," Public Works, 101(5):76-78, 138 (May 1970).
After conducting a literature search on gas production in
refuse disposal sites, the author presents a broad discussion of
landfill gases, some case histories of construction problems on
landfills, and a very good list of gas control recommendations.
Most studies indicate carbon dioxide is the principal gas
produced in landfill degradation, and maximum concentrations are
usually reached early in landfill life. Methane gas can also attain
17
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high concentrations, but this usually occurs after the carbon dioxide
peak is reached. Hydrogen sulfide has been a problem in areas
where sea water has been allowed to enter the fill. Small quantities
of hydrogen and carbon monoxide have also been noted.
Because gas production will continue for many years, the
author suggests several excellent points to ensure safety in dwellings
constructed on landfills. He recommends that:
1. Vents be installed in the fill to bleed away the gases when slight
pressures develop. These can simply be perforated pipes driven
into the fill and open to the atmosphere.
2. In addition, a granular material such as crushed stone, gravel,
slag, or sand be placed over the fill to encourage uniform diffu-
sion of gas into the atmosphere.
3. Structures designed for sanitary landfills be constructed with
gas-tight membranes beneath the ground floor slab. Ordinarily,
a well-constructed polyethylene membrane, preferably in two
layers and laid on a clear sand fill, will be sufficient. Care
must be taken that the fill is not coarse enough to puncture
the membrane during construction.
4. Care be taken to provide vapor barriers around all breaks in
the foundation.
5. The design eliminate any pockets, depressions, or unwanted
dead areas beneath or around the structure where gas might
accumulate.
6. When structures are built adjacent to a sanitary landfill,
garbage dump, etc., special precautions be taken to prevent
the channelling of combustible gases from these areas.
7. If there is a possible hazard in a closed area, it be ventilated
to keep the combustible contents in the atmosphere below the
lower limit of flammability (natural ventilation is adequate for
methane concentrations of less than 1 percent; forced ventila-
tion is advisable where methane concentration is greater than
1 percent).
"Measuring Gas Escape from a Landfill," Public Works, 95(9):
163 (Sept. 1964).
To measure the carbon dioxide escape from landfill cover, a
device was developed incorporating copper wool saturated with
potassium hydroxide to absorb any carbon dioxide escaping from
the fill cover. Additional weight of the absorber represented carbon
dioxide collected over a given time period. However, the amounts
collected in test runs did not agree with theoretical diffusion
equations for carbon dioxide escaping to the atmosphere. Refine-
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ments were being made to the device and measurements were to
continue. The device was expected to be useful in determining the
necessary thickness of landfills. (OR)
This brief article completely describes this unique sampling
device and how it works.
MERZ, R. C., Investigation to Determine the Quantity and Quality
of Gases Produced During Refuse Decomposition, Final Report,
Los Angeles, University of Southern California, Department of Civil
Engineering (Aug. 1964).
In laboratory experiments in which eight'55-gallon drums were
filled with garbage, paper, and grass, researchers at the University
of Southern California measured the quantity and determined the
composition of the gases produced by the decomposition of the
material in the drums over a 9- to 11-month period.
Results of the experiments showed that the volume of gas
production is definitely related to the moisture content of refuse.
Gas production generally was higher in drums that received the
larger amounts of water. The volume of gas production also
varied with the amount of grass and garbage in the refuse. Aerated
drums produced more gas than did those not aerated.
The greatest percentage of the gases was in the form of carbon
dioxide and nitrogen. The amount of carbon dioxide production
increased in volume as the tests continued. Methane was not found
in measurable volumes in the drums. (UC)
MERZ, R. C., and R. STONE, Factors Controlling Utilization of
Sanitary Landfill Site. Final Report, Research Grant UI 00518,
Department of Health, Education, and Welfare, unpublished (July
1963).
Five 20-foot-deep refuse cells were placed partially above grade
in a virgin area at a southern California landfill site. A sixth cell
was placed entirely above grade and allowed to remain aerobic.
Refuse was placed in the cells under varying conditions of moisture
content and compaction. All cells were monitored for gas generation
at depths of 6 and 15 feet.
The gases produced within the anaerobic cells consisted chiefly
of carbon dioxide and nitrogen with varied concentrations of
methane depending on refuse moisture content. Surface irrigation
markedly increased methane production. The gases were found to
diffuse from the cells laterally and downward into the soil and
upwards through the cover material. Landfill gas pressures as high
as 13 inches of water were recorded. The report includes many
tables and graphs explaining the gas concentration histories of the
test cells.
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MERZ, R. C., and R. STONE, "Gas Production in a Sanitary Land-
fill," Public Works, 95(2):84-87, 174, 175 (Feb. 1964).
The authors report on their 3-year study of landfill gas
problems. Among the statements and conclusions from this field-
scale landfill project are:
1. Gases produced within the anaerobic test landfills consisted
chiefly of carbon dioxide and nitrogen. The concentration of
methane depended on moisture content and varied from little
more than a trace in the landfill to which no water was added
to the major component (greater than 50 percent) of the gas
produced in a saturated landfill. Only very small amounts of
hydrogen were present.
2. Gases produced in the aerobic fill consisted chiefly of carbon
dioxide and nitrogen. Oxygen did not exceed 10 percent.
3. Methane production increased markedly with surface irrigation
of the fill.
4. Gases within the four landfills appeared to be under positive
pressure and diffused laterally and vertically downward into
the surrounding earth as well as upward through the top cover.
5. Small concentrations of oxygen were frequently found in all
fills.
6. Initial peak temperature was reached in 3 months and occurred
at various depths. Temperature peaks reached during the latter
stages of the decomposition were never as high as the original
peak.
7. Initial temperatures in the aerobic fill greatly exceeded those
in the anaerobic fills. (UC)
MERZ, R. C., and R. STONE, "Quantitative Study of Gas Produced
by Decomposing Refuse," Public Works, 99(11): 86-87 (Nov. 1968).
In this article, the authors describe the results of a field
study in which approximately 15 tons of refuse were encapsulated
in a 10,000-gallon underground storage tank. In the filling process,
a 6-inch layer of sand was placed in the bottom of the tank; then
refuse was added and a gas-sampling pipe installed. The refuse
consisted of paper (42 percent), grass and garden clippings (38
percent), plastic (3 percent), glass (5 percent), metal (7 percent),
and dirt (5 percent). Water was added to bring the moisture content
to 69.9 percent (dry weight basis). The in-place density of the refuse.
was 634 pounds/cubic yard. After filling, the top of the tank was
sealed.
About 39.3 cubic feet of gas were produced during the first 3
days after sealing. However, gas production was negligible by the
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end of 60 days and continued so until about the 230th day. There-
after, production was resumed, and a total of 2,025 cubic feet of
gas were produced during the period 230 to 530 days after initiation.
Production again dropped after the 550th day and from the 550
to 750 day was about 27.5 cubic feet gas/cubic yard refuse.
The temperature ranged from 78 to 100 F during the first
300 days, and from 105 to 120 F during the period of 350 to 475
days. The deep level (14 feet) temperature probes failed during the
later stages of the study; hence, no firm figures are available for that
period. (UC)
MERZ, R. C., and R. STONE, "Sanitary Landfill Behavior in an
Aerobic Environment," Public Works, 97(1):67-70 (Jan. 1966).
An aerobic landfill test cell was constructed and was provided
with an access well in which outlets for gas collection lines, leach
collection lines, and electrical leads could be located. The researchers
also gained access through the well to place equipment and obtain
data.
A piping system to admit air also was installed. To prevent
the air from being forced through the earth cover into the atmos-
phere, an impervious polyethylene membrane was stretched 1 foot
below the surface. The total rate of settlement over 344 days was
1.66 feet, a shrinkage four to six times greater than that occurring
under anaerobic conditions.
The chief components of the gas taken at the top and bottom
levels were nitrogen, methane, oxygen, and carbon dioxide. At
times hydrogen was detected. The temperature was higher and had
a greater range in the aerobic cells than in the anaerobic cells.
In the former, it ranged from 113 to 193 F at the 10-foot level.
Gases discharged from both aerobic and anaerobic cells had an
objectionable odor. (UC)
MERZ, R. C., and R. STONE, Special Studies of a Sanitary Land-
fill, Final Summary Report, Distributed by National Technical
Information Service, Springfield, Va., 22151, as PB 196 148 (1970).
Scientific field investigations were conducted to determine
among other things the quality of gas produced in landfills and the
volume of gas produced by a known refuse quantity. The experi-
ments were conducted in four test cells: A and B were under normal
anaerobic conditions, C was equipped with a mechanical aeration
system, and D was placed in a large steel tank and sealed. Varying
amounts of water were added to cells A and B.
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After 2 years, cells A and B were generating gas with equal
concentrations (nearly 50 percent) of carbon dioxide and methane.
Cell C during aeration was found to emit little carbon dioxide or
methane but high concentrations of oxygen and nitrogen. Cell
D contained 73 cubic yards of refuse and produced 2,027 cubic
feet of gas over 907 days. Coring revealed extensive decomposition
in the aerobic cell (C), but little decomposition in the two anaerobic
cells (A and B).
"Methane Gas Explosions Delay Building on a Landfill," Solid
Wastes Management Refuse Removal Journal, 12(7):20 (July
1969).
The article describes an accident in Atlanta, Ga., which was
caused by the explosion of an accumulation of methane gas
generated by anaerobic decomposition of refuse. Two workmen
were killed and four others escaped with minor injuries. The men
were working in a building located in a recreation center. In 1961
the area around the building was used as landfill, and as a con-
sequence, the level of the ground was raised several feet. The
original structure was 90 feet long by 40 feet wide, one story high,
and had a 17-foot-high basement. As a part of the renovation of
the building, all windows in the basement were bricked up and
the land around the building was filled to the level of the first
floor. Except for one stairway all entries between the first floor
and the basement were closed. The opening was fitted with a tight-
fitting trap door. Later, the entire floor was covered with tile.
The explosion occurred later when gas piping was installed.
All gas connections and appliances had been found to be gastight.
A workman noted a draft coming through the casing around a gas
pipe. The explosion occurred when a plumber was in the process
of lighting a cigarette. Later investigation ruled out the possibility
of leakage from the gas pipes and furnished convincing evidence
that methane coming from the surrounding landfill had accumulated
in the building.
The article also mentions another explosion resulting from
methane escaping from a reclaimed dump. This explosion ripped
apart a swimming pool under construction in Montreal, Canada.
Geologists claim that solid wastes in a landfill ordinarily take from
10 to 25 years to decompose. (UC)
ROGUS, C. A., "Use of Completed Sanitary Landfill Sites," Public
Works, 91(1): 139-140 (Jan. 1960).
Since 1898, New York City has landfilled about 300,000,000
cubic yards of material; about 10,000 acres of tidal and marshy
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lands have been reclaimed. As the refuse decomposes, hazardous
methane gas may be generated and escape from the landfills
through cracks in the cover material. Since the decomposition
process is very slow, the methane gas hazard may persist for many
years. For this reason, the city requires that all buildings erected
on completed landfills be protected from methane gas by using
gastight construction and adequate ventilation.
The author sets forth a good list of minimum gas-control
construction requirements for residences, multiple dwellings, and
industrial and commercial buildings.
"Sanitary Landfill Tests Investigating Refuse Volume Reduction
and Other Phenomena," SED Research Report No. 21, Journal of
the Sanitary Engineering Division, ASCE, 83(SA6):Paper 1853:1-3
(Nov. 1958).
At the Union Bay sanitary landfill disposal site, Seattle,
Wash., tests have been performed over a 1-year period to ascertain
compaction, settlement, fill temperature, and gas production.
These data are critically reviewed with reference to obtaining
optimum refuse disposal volume into a given landfill area.
Relatively large quantities of combustible methane gas and
some carbon dioxide gas were reported to be generated in the fill.
Analyses indicated that a fraction of less than 1 percent other
gases were also continuously evolved throughout the test year.
Most gas production occurred 6 to 24 months after the landfill
was in place. Landfill areas receiving additional moisture and con-
taining greater refuse fill depths were reported to have increased
gas production.
SETTER, L. R., "Gas Sampling Device for Sanitary Landfill Investi-
gation," Public Works, 70(9):45-46 (Sept. 1939).
A gas sampling device was developed for use in New York
City's landfills. Having a rigid construction, the device was driven
into the refuse with a mallet. The sampler worked quite well and
prevented air from entering the gas sample. A cross-sectional
drawing and complete description are included.
SOWERS, G. F., "Foundation Problems in Sanitary Landfills,"
Journal of the Sanitary Engineering Division, ASCE, 94(SA1):
103-116 (Feb. 1968).
Landfill gases have caused explosions, serious vegetation kills,
and sickness to overexposed persons. Proper foundation design
can control gas. Perforated pipes driven into the fill serve as
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vents to bleed away the gases. Gastight membranes (two layers
thick) spread over vented porous sand serve as good barriers under
ground-floor slabs.
The author touches on a variety of construction problems
caused by landfills.
STONE, R., E. T. CONRAD, and C. MELVILLE, "Land Conser-
vation by Aerobic Landfill Stabilization," Public Works, 99(12):
95-97, 138, 140 (Dec. 1968).
The paper reports results obtained in a demonstration project,
which was to demonstrate acceleration of the stabilization in a
process in which compacted refuse is aerobically decomposed
before final disposal. In the study, a large cell or pit (200 feet
long by 50 feet wide by 17 feet deep) was used. It was underlaid
with a series of gravel-covered perforated pipes through which air
was forced by means of a 1,200 cfm (under 10 inches of water)
blower. After the refuse had been aerated for a specific length
of time, the "relatively stable" residue was transferred from the
aeration pit to a final residue cell where it was compacted again
and covered with soil, as is done in conventional sanitary landfill
operations. Here anaerobic decomposition took place.
The test material consisted of domestic rubbish and garbage.
The aforesaid refuse was about 45 percent (by wet weight) paper
or paper in origin, about 45 percent tree and garden trimmings,
and about 10 percent garbage. The organic content was about 85
percent, and moisture content ranged from 35 percent in the fall
to 80 percent in the spring.
Filling of the first test cell began in June 1967. The filled
cell contained 2,940 tons of compacted refuse (overall density—
1,253 pounds/cubic yard wet weight). No soil cover was used in
the first test; however, one was used in the subsequent tests. The
blower cycle during loading (2 months) was 55 minutes on, 35
minutes off, and thereafter (P/2 months) 70 minutes on, 20 min-
utes off. The aeration rate ranged from 225 to 310 cubic feet/
cubic yard refuse/day.
Temperatures rose as high as 190 F in the test cell. During
the aeration period, the composition of gas samples taken from
the cell varied as follows: carbon dioxide from 3 to 19 percent;
oxygen from 7 to 17 percent; nitrogen from 67 to 80 percent; and
methane from zero to a trace. During the aeration stage in the
first run, a fire occurred in the cell contents. Whether or not the
fire had an internal or external origin could not be determined.
To exclude future external origins, the cell was covered with soil.
No fires occurred after the soil cover was used.
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At the end of 6 months, the aeration was discontinued and
the material was allowed to revert to the anaerobic state. When the
gas was measured from the several probes during the next 3-month
period, carbon dioxide percentage increased to a range of 57 to
85 percent; oxygen dropped to 0 percent; nitrogen declined to
between 1 to 12 percent; and methane rose to a range of 2 to 42
percent. Excluding refuse lost by way of the fire, the volume
reduction during the 10-month aeration-nonaeration period was
approximately 1,100 cubic yards-that is, slightly less than one-
fourth of the original volume. (UC)
U.S. ENVIRONMENTAL PROTECTION AGENCY, Development
of Construction and Use Criteria for Sanitary Landfills, Final
Report, p. III-l to 111-29, unpublished (1971).
This report is on a 3-year gas movement and control study
conducted by Los Angeles County, Calif. It contains valuable
information on the application of gas control systems.
A gas movement field study was conducted on 10 completed
landfills. Information was gathered on soil grain size distribution,
classification, specific gravity, dry density, and moisture content
at the test sites. Gas probes were installed at each location, and the
gases were analyzed for carbon dioxide, oxygen, nitrogen, methane,
and hydrogen sulfide concentrations. The report includes complete
descriptions of each site; a description of the gas probes and
sampling techniques used; and diagrams, tables, and graphs showing
gas movement patterns and gas concentration gradients.
The second part of the gas movement study was a laboratory
experiment to determine the gas permeability characteristics of a
limited range of soils. Methane diffusion-dispersion coefficients
were developed for four soil types, each tested at two moisture
levels. The results of the experiment indicate the rate of movement
of methane by diffusion-dispersion is slower through soils with
fine particles than through those with coarser particles for both
air-dry and optimum moisture conditions. A complete description
of the laboratory apparatus and a table of results are included.
The control of gas movement can be accomplished by using
physical barriers or ventilation devices. Barrier devices involve
placing some membranes or other substances between the refuse
in the landfill and the adjacent soils. Ventilation devices involve
the release and venting of gases from or beneath a building. Gas
control systems were installed at three of the 10 test sites:
1. Five wells, 30 inches in diameter and 60 feet deep, spaced
at 40-foot intervals. Wells were divided into three levels, gravel
filled, and each level topped with concrete. Three 6-inch
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diameter pipes were installed in each well. These pipes were
attached to an 18-inch header which was evacuated by a 25-
horsepower blower.
2. A venting system under a 12- by 25-foot greenhouse. Four
inches of gravel were placed over 3-inch-diameter perforated
pipes. The gravel and pipes were sealed with an airtight
covering of asphalt. The pipes were then vented to the
atmosphere.
3. A 750-foot trench, 2 feet wide by 6 feet deep with two
24-inch-diameter, 50-foot-deep wells drilled 200 feet apart
directly below the trench. Perforated pipe was placed in the
wells and trench, and the entire system was filled with gravel,
capped with concrete, and vented to the atmosphere.
The report includes schematics of these systems and descrip-
tions of the test run on them.
ZABETAKIS, M. G., "Biological Formation of Flammable Atmos-
pheres," Report RI. 6127, Washington, U.S. Department of the
Interior, Bureau of Mines (1962).
The Bureau of Mines Explosives Research Laboratory has
investigated six potentially hazardous situations where combustible
gases were produced by bacterial action on organic materials. Four
of these hazardous situations resulted from the decomposition of
landfilled refuse. The recommended controls for relieving hazards
in buildings were forced or natural draft venting and gastight
foundation construction. A short description of each incident is
included.
In each of the six incidents, the hazardous gases were created
by the anaerobic decomposition (fermentation) of organic matter.
The methane-producing bacteria utilize fatty acids, alcohols,
acetone, hydrogen, carbon dioxide, etc., to produce methane.
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BIBLIOGRAPHIES AND ABSTRACTS
USED AS REFERENCES
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Black, R. J., J. B. Wheeler, and W. G. Henderson, Refuse Collection
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