Walker Environmental Group
Constructing a Landfill
How do you construct a landfill?
Generic Double Composite Liner
Waste Primary Leachate Collection System -
Construction of a landfill starts from the bottom up, in layers:
Primary Composite Liner Secondary Leachate Collection System Secondary Composite Liner -
Attenuation layer
- Collection pipes
- 0.3m Gravel
- 1.5mm HDPE Liner
Attenuation Layer -
• The attenuation layer is the base of the landfill.
• It is a layer of natural or constructed low permeability soil.
- 0.75m Engineered Clay Liner
Aquifer -Bedrock -
- 0.3m Gravel
- 2.0mm HDPE LINER
(groundwater source)
- 0.75m Engineered Clay Liner
Double composite liner
- 1m Natural or Constructed
Low Permeability Soils
• Like a plastic pool liner, the landfill liner stops leachate
from passing through into the earth.
• It is a composite of two plastic liners and two clay liners.
Secondary liner and leachate system
• The secondary liner is a back-up constructed to provide redundancy and
contingency to the system.
• Liner construction begins with a layer of compacted or engineered clay.
• The plastic liner is rolled out on top of the clay and fused together.
• The secondary leachate system is placed on top of the plastic liner.
Primary liner and leachate system
• The primary liner and leachate collection system is constructed on top of
the secondary liner in the same way - clay, plastic liner, leachate system.
What is leachate?
• Leachate is the liquid produced when it
rains on the landfill and the rain washes
through the waste to the bottom. It
becomes dirty as it passes through the
Leachate
lagoon
with
mixers
to
aerate
the
waste.
leachate, preventing odours from forming.
• It is treated at the municipal waste water
treatment plant with other sewage from our homes and businesses.
• The leachate is tested regularly to make sure it meets the municipal
sewer use by-law.
Leachate system:
• The collection system consists
of perforated pipes on top of
the plastic liner, surrounded by
specialized stone.
• The stone layer promotes the
movement of water.
• The pipes have holes in them
so the leachate can enter.
• The liner of the landfill is
sloped so leachate moves by
gravity to a pumping station.
• The leachate is pumped to the
leachate lagoon.
• From there, it is discharged
to the sanitary
sewer.
Perforated pipes
Stone for leachate system
www.walkerind.com
Walker Environmental Group
Constructing a Landfill
Beginning to fill the landfill
• A landfill is constructed as waste disposal volume is required, cell by cell.
• A landfill cell is a small area of landfill capacity that has been engineered
to receive a specific volume of waste.
• One cell in the South Landfill is predicted to take about one year to fill.
• Once cell construction is completed, the landfill
cell is ready to receive waste, as reviewed and
approved by the Ministry of the Environment.
Haul Route
An important part of
landfilling is to have
roadways that can carry
loads to the landfill.
• It is important that waste is placed on top of the
liner fairly promptly to protect the liner.
Long haul trucks have a
designated truck route to
the site.
• A layer of uncompacted garbage is best for this.
The designated route for
the South Landfill keeps
trucks on major highways
and minimizes the number
of residences they pass on
their way to the site.
Building it right: monitoring construction
South Landfill
99 A third party professional engineer who specializes
in landfill design and construction oversees the
construction.
99 A detailed Quality Assurance/Quality Control
(QA/QC) monitoring program is applied to the
construction of the landfill site. The company
that oversees the quality of construction is an
independent engineering firm unrelated to Walker
or to the construction engineer.
99 The QA/QC consultant ensures the appropriate
construction methods have been employed, the
quality of the plastic liner meets the specifications,
the aggregate used in the leachate layer meets
specifications and the clay liner has the appropriate
moisture content and compaction rate.
99 The construction is monitored and approved by the
Ministry of the Environment.
www.walkerind.com