TOPIC 7-LESSON 1Rehabilitation and safe use of previously contaminated sites

INTRODUCTION

Society produces large amounts of waste which have to go somewhere. Where do we put it? How does it affect the environment?

If we have to impact the environment, how do we minimise that impact to an acceptable level?

WHERE DO WE PUT OUR WASTES?

The millions of tonnes of waste our society creates each year has to go somewhere. Some can be recycled, but what about the rest? In most cases it goes to a dump.

WHERE DO WE PUT OUR WASTES?

Waste dumps or landfills can either be a depression carefully designed and built or an old mine site with the appropriate geology.

WHERE DO WE PUT OUR WASTES?

The most significant factor to consider in selecting a dumping ground is the geology that lies beneath the surface. The landfill must be sealed in such a way that any materials it contains cannot leak into the subsurface water system or surrounding rocks or soil.

WHERE DO WE PUT OUR WASTES?

Faulting and fracturing destabilise the rock and make ground water movements unpredictable. Fractures allow spaces for water to travel which could carry wastes into ground water.

WHERE DO WE PUT OUR WASTES?

Porosity and permeability of the rock also need to be evaluated. Different rocks have different crystal structures which can lead to differences in the amount of water that can pass through them.

What type of bedrock would create a good waste dump site?

WHERE DO WE PUT OUR WASTES?

The landform of the surface (geomorphology) is another very important factor when considering the location of a waste dump.

Why do you think hilly sites should be avoided?

WHERE DO WE PUT OUR WASTES?

Old mine sites are now being assessed for waste sites. If you think about it, an open cut mine would be an ideal place to dump wastes. However, we must consider the geology before we consider a site appropriate.

WHERE DO WE PUT OUR WASTES?

For example the Woodlawn mine in Goulburn NSW, now no longer operational, is being considered. As a result of years of open-pit mining operations a huge hole has been left in the ground.

WHERE DO WE PUT OUR WASTES?

The mine is located in an environmentally sensitive area. What does this mean? It’s near an elevated ridge that provides a water shed (drainage system) for Canberra’s water on one side and Sydney’s water on the other.

WHERE DO WE PUT OUR WASTES?

When the mine was operational special measures had to be done to ensure waste from the mine site was not leeching hazardous material into the ground water supply.

Today, the Sydney Catchment Authority has advised that the site is suitable and water tight..

WHERE DO WE PUT OUR WASTES?

What do you think some of the effects would be if we began dumping wastes in this area and 10 years down the track discovered that hazardous materials were leeching into the ground water?

WHERE DO WE PUT OUR WASTES?

Landfills must have some method in place to collect water that has filtered down through the wastes. Otherwise the depression would fill up with water.

WHERE DO WE PUT OUR WASTES?

The liquid that eventually reaches the bottom of the pit (leachate) is usually contaminated. Most landfills are designed to have a sloped base with collection pipes attached to the lower end to collect the leachate which can then be treated and disposed of appropriately.

WHERE DO WE PUT OUR WASTES?

It’s very important that the leachate does not reach the water table because this could have huge implications to water supplies.

WHERE DO WE PUT OUR WASTES?

When the landfill is full, it is then covered up to prevent water from getting in and creating more leachate. This cover is usually several layers of plastic and clays to prevent water getting in and also overlain with sandy soil to allow water to run off the top.

WHERE DO WE PUT OUR WASTES?

A layer of topsoil and vegetation is then placed on the top and the area can then be used for normal activities.

Do you think there may be any problems with this system?

WHERE DO WE PUT OUR WASTES?

A major concern is that the landfill fails to seal. Plastic liners and clay layers do not always provide a perfect seal and can allow water to pass through them. Landfill covers can also be breached allowing water to infiltrate into the waste.

WHERE DO WE PUT OUR WASTES?

Another common problem is subsidence. When the contents of the landfill decay and break down, they settle and compact further. This can affect the cover and structures built on top of the site.

WHERE DO WE PUT OUR WASTES?

For these reasons landfill sites are monitored very carefully both while they are being filled and well after they have been covered.

HOMEWORKRead page 161-162 HSC Spotlight Text

Update electronic vocabulary

Complete DOT Point 7.1 pg 81

TOPIC 7-LESSON 2Rehabilitation and safe use of previously contaminated sites

METHODS OF DISPOSAL

We’ve just discussed where our waste goes, but what are the methods that get it there? What happens to your rubbish that you place in the bin?

METHODS OF DISPOSAL

The management of waste has become a major concern for not only Australia but the rest of the world.

Why do you think this has become such a serious problem?

METHODS OF DISPOSAL

Household wastes (putrescible wastes) consist mostly of food and garden waste, paper, glass, plastic, metal and miscellaneous materials. Most can and should be recycled but often is not.

How do you dispose of your waste at home?

METHODS OF DISPOSAL

Waste management centres operated by Waste Services NSW provide centres for waste collection for householders, councils, commerce and industry. These centres accept materials that can be recycled, processed or in need of disposal.

METHODS OF DISPOSAL

The following pre-sorted materials are accepted free of charge: Paper, newspaper, cardboard, milk and juice

containers Recyclable plastics, aluminium and steel cans,

bottles and jars Scrap metals, fridges, stoves, washing machines

and the like Sump oil, paints, paint thinners and cleaners (up

to 20 litres) Car bodies (at some depots)

METHODS OF DISPOSAL

The following materials can be disposed of at management centres for a fee:

Garden waste such as garden clippings, weeds, prunings and small tree branches

Untreated timber, pallets and crates Reusable items such as lawn-mowers, bicycles

and furniture at some depots

METHODS OF DISPOSAL

Some centres collect and properly dispose of household chemicals. It’s important that such chemicals are not poured down the sink or put in common garbage. Pestacides Herbicides Fungacides Weed killer Baits Acids Alkalis mercury

METHODS OF DISPOSAL

Why do you think it’s important to dispose of household chemicals appropriately?

Consider this:½ a teaspoon of pesticides such as chlorpyrifos

or diazinon will make the volume of water required to fill an olympic pool toxic.

METHODS OF DISPOSAL

The material that goes into a landfill must not contain dangerous wastes. Such items are dealt with specifically. For example, hazardous material such as biomedical wastes are incinerated or sterilised by microwave radiation or autoclaves.

METHODS OF DISPOSAL

Liquid wastes, is deemed neutral, are discharged directly into drains. However most need to be treated in some way by liquid waste specialists before being disposed of.

METHODS OF DISPOSAL

Chemicals like acids, solvents and bases (hazardous wastes) need to be treated to make them un-reactive. This is usually done by reacting them with appropriate chemicals until a safe by-product is created.

If the product is neutral and safe it’s tipped down the drain. If not, it’s usually treated again to remove any water and then disposed of in landfills, incinerated or stored at special facilities

METHODS OF DISPOSAL

Highly toxic (intractable) wastes are contaminated soils, sludges and radioactive. There is a range of options for their disposal once treated.

REVIEW

Guidelines for the treatment and disposal of wastes are very important and necessary for maintaining public health and environmental problems.

What do you do to ensure proper disposal of your wastes?

HOMEWORKRead pages 162-163 HSC Spotlight Text

Update electronic vocabulary

Complete DOT Point 7.2

TOPIC 7-LESSON 3Rehabilitation and safe use of previously contaminated sites

RECYCLING

Recycling involves processing used materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from landfilling) by reducing the need for "conventional" waste disposal, and lower greenhouse gas emissions as compared to virgin production. (http://en.wikipedia.org/wiki/Recycling)

RECYCLING

The government is committed to implementing strategies that reduce waste. Most of our household waste can be recycled.

RECYCLING

There is no limit to the number of times glass can be recycled. In Australia 43% of our glass is recycled. For every 1 tonne of waste glass recycled, 1.1 tonnes of raw materials are saved.

RECYCLING

Steel is considered to be the most recyclable product in the world. Yet in Australia we only recycle about 35% of the steel we use every year. Steel cans that can be recycled include: Pet food cans Food cans Coffee Oil Paint and aerosol cans Bottle tops Jam jar lids

RECYCLING

Milk and juice cartons, aluminium cans, plastics and paper can all be recycled. These items make up nearly half your household waste.

RECYCLING

Food scraps, grass and garden clippings and wood (greenwaste) makes up nearly the other half of household waste and can all be recycled. If this material makes it to landfills it decomposes and creates flammable greenhouse gases and leachate along with taking up space.

RECYCLING

Imagine the impact on the environment if every person recycled their household waste appropriately.

What do you think the results would be? What do you think could be done to get more people to recycle?

ACTIVITY

Complete activity 3.14 pg 164 together in class

HOMEWORKRead page 163 HSC Spotlight Text

Update electronic vocabulary

Complete DOT Point 7.3

TOPIC 7-LESSON 4Rehabilitation and safe use of previously contaminated sites

MINE SITE REHABILITATION

We depend on minerals extracted from the ground to produce every day commodities. To minimise environmental effects of mining alternate products have been invented, more efficient means of production have been developed and recycling levels have increased.

MINE SITE REHABILITATION

Rehabilitating the mine site is also now mandatory for mining organisations. Careful managed rehabilitation programs are put into action to help restore the area to its original or similar state.

We saw first hand an example of this on our flinders trip. Why do you think it’s important?

MINE SITE REHABILITATION

Mining companies spend a lot of money ensuring rehabilitation regulations are met and often exceeded. The basic procedures mining companies follow are listed below: Exploration and discovery of the mineral Community consultation Develop environmental impact statement Seek approval from state government Establish animal shelters, seed collection, top soil

removal and storage to ensure successful rehabilitation Mining Replace topsoil, reshape landforms and plant seeds

collected earlier Final rehabilitation of mine back to previous land use or

modified new productive land use

MINE SITE REHABILITATION

A lot of work goes into rehabilitation programs. This happens before, during and after mining operations. In early days of mining in Australia there was no such thing as rehabilitation.

MINE SITE REHABILITATION

Mining took place with little to no regard for the environment. And once the mining was complete the site was deserted.

What are some of the problems this would have resulted in for the environment?

MINE SITE REHABILITATION

Some of these old mines are now being rehabilitated and governments now require rehabilitation methods to be planned prior to mining.

ACTIVITY

Start reading the rehabilitation Case Study of Peelwoodmine together (TAFE/OTEN Book). Students are to finish this as homework

HOMEWORK

Read pages 164-165 HSC Spotlight Text

Update electronic vocabulary

Finish reading rehabilitation Case Study of Peelwood and answer questions that follow

Complete ‘To Think About’ pg 166-170 HSC Spotlight Text

TOPIC 7-LESSON 5Rehabilitation and safe use of previously contaminated sites

POP QUIZ

Students are to complete the quiz during class.