Philadelphia University
Faculty of Engineering
Department of Civil Engineering
First Semester, 2013/2014
4-Landfills
4.1 Introduction
4.2 Planning
4.3 Classification
4.4 Sound technical options
4.5 Additional considerations
4.6 Conclusion
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4.1 Introduction
• The ultimate storehouse of a city's MSW
• In some cases, landfill is the only MSWM
option available
• Effective operation depends on planning,
administration, and management of MSWM
system. (Institutional, policy, regulations)
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4.2 Planning
Key considerations in landfill planning
Required capacity
Not In My Back Yard (NIMBY)
Hydro-geology
Cost
Post-closure land use
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Required capacity:
• Capacity refers area and volume required
over the useful life
• It depends on the generation rate, rate of
population growth, density and waste
compacted at landfill and maximum in-place
elevation.
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Not In My Back Yard (NIMBY):
NIMBY refers to community opposition to the
sitting and operation of MSW facilities close to
their neighborhood. Residents concerns include:
Health and environmental risks;
Negative impact on aesthetics in the area;
Lowering of property values;
Increased traffic, noise and dust; and…
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Hydro-geology:
Include water table, hydrological conductivity of
the soil, surface water, precipitation and others;
ideally, landfill should be sited in an area:
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Hydro-geology:
 Low hydrological conductivity with low water
table
 Landfills should not be sited in wetlands, to
avoid contamination ecologically sensitive areas.
 Landfills should not be sited in floodplains, to
minimize the risk of waste washout during
flooding.
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Costs:
The costs may be broken into:
 Capital costs which often determine the type of
facility that can be constructed.
 Operating costs of the facility
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Planned post-closure use:
Post-closure use will have an impact on how
the land is developed during use as a landfill.
• Planned heavy building construction
require the use of high density compaction
equipment
• Recreational uses planned, as golf courses
or parks, site must be graded with
vegetation replanted on closed areas of the
operating facility.
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4.3 Classification
Three general categories:
1. Open dumps
2. Controlled dumps
3. Sanitary landfills
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Open dumps and the need to upgrade them
 Due to the low initial costs of open dumps, and
lack of expertise and equipment, these sites are
common in developing countries.
 Significant risks to human health and the
environment,
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Open dumps and the need to upgrade them
 Remediating cost can easily exceed their total
lifetime capital and operating costs.
 Contaminated groundwater may never be
returned to usable condition
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Open dumps and the need to upgrade them
 Open dumps attract birds that feed on the
wastes, which can make serious disease vectors
than flies or rodents.
High need to upgrade open dumps and construct
new controlled landfills in developing countries.
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4.4 Sound technical options
Planning landfill phases are:
1. Sitting
2. Design
3. Construction, operation, and
environmental monitoring
4. Closure and post-closure.
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Sound practices for MSW landfills
• Leachate management and
environmental impact minimization
• Gas management and risk reduction
• Secure access and maintenance of
gate records
• Compaction and daily cover
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Sound practices for MSW landfills
• Documented operating procedures,
and worker training and safety
programs
• Establishment and maintenance of
good community relations
• Closure and post-closure planning
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Sitting
Sitting can be one of the most difficult
processes in the landfill process. The main
considerations are:
• Capacity
• Public involvement in the sitting process
• Hydro-geology/cover material
• Access
• Proximity to airports
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Capacity:
Available land area to minimize costs
associated with design, permitting, sitting, and
closure and post-closure requirements, Ideally
capacity for 10 - 20 years of operation in case
of sanitary landfills.
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Public Involvement:
The planner must be prepared to involve
potentially affected communities in the sitting
process.
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Hydro Geology:
It is desirable to take advantage of the geology
of a site (types of soil and rock)
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Sitting guidelines related to hydro-geology
Do not site landfills:
• in wetlands or in an area with a high
water table;
• in floodplains;
• in areas that are close to drinking
water supplies; or
• Along geological faults or areas which
experience frequent seismic activity.
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Sitting guidelines related to hydro-geology
Do site landfills:
• above clay soils;
• above igneous rock; and
• where cover material is available
nearby.
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Cover material.
The compacted MSW must be covered by
15-30 centimeters of soil at the end of each
day's operations. The availability of cover
material is also an important consideration in
the sitting decision.
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Access:
The ideal location would therefore be
sufficiently far from the city to allow for future
population growth, but close enough to be
reasonably accessible.
The roads that provide access to a landfill
must be adequate to handle the types and
quantity of vehicles that will be used.
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Proximity to Airports:
A landfill should not be sited closer than two
kilometers from the nearest airport. Birds
converging at the landfill may pose a problem
for aircraft
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Other Considerations:
Sloping area will facilitate leachate collection.
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Landfills should not be sited:
• in very windy areas,
• near existing gas, sewer, water, or
electrical lines,
• near residential areas, churches, schools,
etc.
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An environmental risk assessment (EnRA)
should be made once the final site is
selected. EnRA should detail the risks to
ground and surface water from the facility, the
risks from gaseous emissions, the impact of
vermin, traffic, litter, and noise on the area and
the potential for recovery of the land after postclosure period.
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In the case upgrading open dump in to a
controlled dump or sanitary landfill, planner
applies the above procedure to the areas for
proposed expansion of the existing site.
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Items for consideration at the design stage
• Capacity
• Public/private ownership/operation
• Monitoring and control of leachate
• Monitoring and control of landfill gas
• Access and tipping area
• Pre-processing and waste picker policy
• Operations and safety manuals
• Closure and post-closure plans
• Community relations program
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Capacity
Controlled Dump: In case of planned
capacity may not be protected by zoning and
land use restriction, the landfill planner must
use the designated site strategically to
minimize the risk of future incursion by
municipal development and maximize the total
area available over the lifetime (acquisition of
property surrounding site)
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capacity
Sanitary landfill: Capacity is granted by
regulatory permits on an incremental basis. So,
planner develops it in two- to five-year
increments once the overall site meets the
required zoning and land use requirements.
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Public/private ownership and operation
In most developing countries landfills are
owned and operated by local governments.
Where expertise is available in the private
sector, municipal planners should explore the
option of privatizing landfill operations on a
contractual basis. This option should be
weighed carefully in bases of cost recovery
and the payment of fees.
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Monitoring and control of leachate:
Leachate management is a key factor in
safe landfill design and operation. The
natural decomposition of MSW and rain
infiltration into the site causes potentially
toxic contaminants. The wetter the climate is
the greater potential risks of ground- and
surface water contamination. The geology of
a site can exacerbate or reduce amount of
leachate.
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Monitoring and control of leachate:
Household hazardous waste (e.g., paint
products, garden pesticides, automotive
products, batteries) and hazardous wastes
from commercial and industrial generators
can release organic chemical and heavy
metals contaminants in leachate.
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Monitoring and control of leachate:
Natural or synthetic materials are used to
line the bottom and sides of landfills to
protect ground and surface water. Two feet
or more of compacted clay, thin sheets of
plastic made from a variety of synthetic
materials and others used in lining landfills.
Natural and synthetic liners can crack, if
improperly installed, or can lose strength
over time.
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Monitoring and control of leachate:
More than one liner or a mix of natural and
synthetic liners, called a composite liner, is a
recommended alternative. To minimize
production of leachate, covering material
should be applied after each day of MSW is
spread.
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Sanitary Landfill (AKA Municipal Solid Waste Landfill)
http://www.epa.gov/garbage/dmg2/chapter9.pdf
SANITARY LANDFILLS (accommodate 57% of total
municipal solid waste):
 Each day trash is spread
in thin layers
 Compacted down
 Covered with a soil layer
 Graded for drainage
Sanitary landfills have largely
replaced open dumps.
http://www.epa.gov/garbage/dmg2/chapter9.pdf
Leachate collection and treatment:
Leachate collection systems are installed above
the liner and consist of a perforated piping system
which collects and carries the leachate to a storage
tank. Periodically, leachate removed from the storage
tank and treated or disposed of.
Most common leachate management methods are:
discharge to wastewater treatment plant, on-site
treatment and recirculation back into the landfill.
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Leachate recirculation
over waste in landfills showed an increase
the quantity (by factor of 10) and quality of
methane gas for recovery as well as possibly
reduces the concentration of contaminants in
leachate and enhances the settling of the
waste.
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Leachate reinjection may be appropriate for
areas with low rainfall. This technology could
be more cost-effective than other treatment
systems.
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possible drawbacks of leachate recirculation
include clogging of leachate collection
systems, increasing release of leachate to the
environment and increasing odor problems.
After weighing these advantages and
disadvantages, federal regulators in the US
decided to allow leachate recirculation only at
landfills that have a composite liner and a
leachate collection system that meets specified
performance requirements.
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At controlled dumps monitoring operations
may involve the scheduled withdrawal of
samples to test for indicator contaminants such
as bacteria, heavy metal ions, and toxic
organic acids.
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Monitoring operations at sanitary landfills may
involve computerized statistical sampling and
automatic reporting of results at the regulatory
agency. Such systems are costly and require
skilled personnel.
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Monitoring and control of landfill gas
Gas management is required at sanitary landfills. At
controlled dumps, it should be monitoring to
determine if dangerous amounts of gas are being
released. A low-cost design (passive collection
system) to handle landfill gas consists of covered
vertical perforated pipes, using natural pressure of
gas to collect and vent or flare it at surface. More
costly active collection systems utilize covered
network of pipes and pumping to trap it. Gas is
processed and used for process heat or electricity.
This collection system is risky and expensive.
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Monitoring and control of landfill gas
Gas management is required at sanitary landfills. At
controlled dumps, it should be monitoring to
determine if dangerous amounts of gas are being
released. A low-cost design (passive collection
system) to handle landfill gas consists of covered
vertical perforated pipes, using natural pressure of
gas to collect and vent or flare it at surface. More
costly active collection systems utilize covered
network of pipes and pumping to trap it. Gas is
processed and used for process heat or electricity.
This collection system is risky and expensive.
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Necessary conditions for economic
capturing of landfill gas
• Sufficient methane is generated;
• Capital is available for processing the gas;
• There is local demand for natural gas or a
means to transport it elsewhere;
and
• The market price for natural gas is relatively
high.
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In many situations, not all of the conditions stated
above are fulfilled, and landfill gas recovery is not
economical.
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These are two enclosed methane flares at a Landfill .
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A county technician checking on a gas collection well
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An example of the electrical generation equipment in one of the Michigan
Cogeneration
System Plants. These engines burn only landfill gas as a fuel and
operate 24 hours a day. Each engine produces 750 kw of electricity
A methane "flare" is used for burning landfill gas .
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Access and tipping area
Fencing should be designed to restrict unauthorized
access to the landfill and to keep out animals. A
staffed gate should be the point of entry to the facility
for vehicles and any waste pickers. Gate should be
equipped with scales for the weighing of vehicles as
they enter and exit the facility. They provide critical
information for planning purposes and for operational
management of collection vehicles.
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Tipping area should be at the working cell. This requires the design of
access roads to these locations within the site.
Pre-processing and waste picker policy
Landfill is the least efficient alternative for materials
recovery operations. Where composting is attractive
at the landfill and/or waste picking activity is
permitted, sorting of the waste should occur close to
the gate or tipping area rather than at the working
cell. Such activities reduce the volume of material to
be landfilled and extend the life of the facility.
Waste picking policy should be established during the
design phase of the facility
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Operations and safety manuals
Manuals should be prepared during the
design phase of the landfill. This permits their
content to be specifically adapted to the
processes for which the facility is designed.
Clear operating procedures and well-trained
workers are vital to safe and effective landfill
operations.
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Closure/post-closure plans
Essential closure and post-closure elements are:
• Plans for the sealing and application of
final cover (including vegetation)
• Plans for long-term leachate and gas
management system monitoring;
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Closure/post-closure plans
• Plans for long-term ground and surface water
monitoring;
• Financial assurance guarantees to the local or
state government; and
• Land use restrictions for the site
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In the case of controlled dumps in most
developing countries, closure and post-closure
plans are not prepared. However, ongoing
monitoring and control of the facility after its
useful life is an unavoidable for periods that
may exceed 30 years after their closure.
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Community relations
The designer should establish a program for
ongoing dialog with community. This should be
based on transparency in landfill operations
and procedures to addressing community
concerns. Some facilities offer give-backs to
their host community.
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