Student Worksheet

What goes on in a landfill site?

Activity 1. Looking at water in landfill

A number of different materials are used in a landfill, each with a different purpose:

Sand – often used beneath the top soil and above the clay capping that is used to cover a full landfill site. It allows excess rainwater water to drain away so that it cannot reach the buried layers of rubbish and soil.
Clay – is used to cap finished landfills to prevent rainwater getting into rubbish and oil layers and which can increase the amount of landfill gas. It is also used to line new landfill pits, so that any leachate does not escape into the surrounding soil or ground water
Soil – is used to cover layers of rubbish each day to prevent odours and scavenging by birds and other vermin. It also allows water from decomposing waste to pass quickly to the bottom of the landfill where it can be removed by leachate pumps.
Gravel – is used around the perforated drainage pipes that collect leachate. It allows the leachate to travel quickly to the pipes without clogging them.

Which of these will be the most porous, allowing water to pass easily? Which will be the least porous? Write your predictions from most porous to least porous below:

1.

2.

3.

4.

Now test it! What you’ll need:

Four 250 ml glass beakers
250 ml of water with five drops of food colouring
100ml measuring cylinder
Stop watch
Garden soil, sand, clay and gravel

What to do

Set up the four beakers half filled and labelled as: garden soil, sand, clay and gravel.
Gently add 100 ml of the coloured water to the top of the material in the first beaker.
Using a stop watch, measure how long the coloured water takes to reach the bottom of the beaker. Record the results.
Repeat the test with the materials in the three remaining beakers.
When complete, work independently to answer the questions below:

What can you conclude from this experiment?

In which material does water travel the quickest?

In which material, the slowest?

How did your predictions compare with your results?

Activity 2. Design and build a 3D model of a landfill

The aim of this activity is for you to build a model that will demonstrate to others how a modern day landfill works. In addition to constructing your model you will also need to provide a 5-slide presentation that answers the following questions and addresses some of the issues involved with modern-day landfill sites.

Your model should answer the following questions:

How does a landfill work?
How is it constructed?
What are the different layers in a landfill? Why are they necessary?
What are the key structures and features found in a landfill site?
How is rubbish added to a landfill?
What are some of the problems of landfills and how are they dealt with (leachate, landfill gas, vermin)?
How is a landfill site rehabilitated after it is filled?

What you’ll need:

Construction materials: e.g. timber, cardboard, paper mache (newspaper, paper mache paste), chicken wire, small cardboard boxes and tubes, masking tape
Gravel, soil, sand, clay
Straws
Paint brushes, paint
Scissors and other craft cutting tools
Small cars and trucks
Computer with Internet access
Diagrams of the layers in a landfill (see Typical Anatomy of a Landfill)

What to do:

Conduct research on the internet about how modern day landfills work in Australia, the different layers in a landfill and the various structures that are found at a landfill site
Draw a plan of your 3D model, roughly to scale
Work out how you will construct the model (size, what you will need, who will do what)
Draw up an action plan, giving the order for the building the model
Build your model and label each feature
Demonstrate your model to some friends and invite feedback about your model
Display your model in a prominent place in the school

Some features that you could show in your model (use your presentation to explain what they do)

Construction

Fences or bunds (mounds of topsoil) around the site
Landfill pit or quarry
Clay liners (at the bottom of the pit and over the entire site after the hole is filled)
Surrounding soil and vegetation
Cells (section of a landfill where the rubbish is dumped, compacted and covered in soil)
Temporary roads into the cells (to allow the vehicles to enter, often made from crushed bricks)

Layers of rubbish

Cover materials for cells (usually sand or soil)
Ground water (beneath the pit)
Ground monitoring system (to test for leakage of any leachate into the surrounding soil or groundwater)
Leachate extraction pipes (surrounded by gravel)
Leachate dams (to store leachate before further treatment or disposal)
Landfill gas extraction wells and pipes (surrounded by gravel)

Operations

Trucks adding cover materials for cells
Bulldozers moving the rubbish around on top of the cell
Heavy vehicles, such as compactors compacting the rubbish
Other features of interest
Residents and businesses bringing trailers or boot loads of waste (rubbish, green waste and recyclables) to be disposed
Trucks delivering rubbish
Weighbridge (to weigh the vehicles before and after entering the site – this calculates the material disposed of at the landfill site)
Transfer station (to sort rubbish, green waste and recyclables)
Trucks dumping rubbish in a cell
Vermin swarming or feeding on the rubbish (birds, cats, foxes, rodents)
Piles of bricks (used to line the temporary roads into the landfill)
Landfill gas powered electricity generators (with electricity lines leading to the grid)