Land contamination is a result of :
The industrial and technological age>> chemicals, machines.
Lack of long-term environmental awareness.
Focus on “now” and “me”, rather than society as a whole
Land Contamination presents a two fold problem :
Avoiding hazards to human health and the environment.
How to proceed from technical and managerial view points.
Contaminated sites are valuable and owners want to develop
them. Environmental activism means we can‟t walk away
from these sites or ignore contamination and just build.
How are Humans Exposed?
There are three major means by which a toxic substance can come into
contact with or enter the body. These are called routes of exposure.
Inhalation (breathing) of gases, vapors, dusts or mists is a common
route of exposure. Chemicals can enter and irritate the nose, air
passages and lungs. They can become deposited in the airways or be
absorbed through the lungs into the bloodstream. The blood can then
carry these substances to the rest of the body.
Direct contact (touching) with the skin or eyes is also a route of
exposure. Some substances are absorbed through the skin and enter
the bloodstream. Broken, cut or cracked skin will allow substances to
enter the body more easily.
Ingestion (swallowing) of food, drink, or other substances is another
route of exposure. Chemicals that get in or on food, cigarettes,
utensils or hands can be swallowed. Children areat greater risk of
ingesting substances found in dust or soil because they often put their
fingers or other objects in their mouths. Lead in paint chips is a good
example. Substances can be absorbed into the blood and then
transported to the rest of the body.
The route of exposure can determine whether or not the toxic
substance has an effect. For example, breathing or swallowing lead
can result in health effects, but touching lead is not usually harmful
because lead is not absorbed particularly well through the skin.
Many paths to exposure
Most dangerous exposure in homes
How Land is Contaminated?
Manufacture of Chemicals (eg paint, pesticides, lead)
Use of Chemicals in Processes (eg hide tanning, power gen)
Disposal or Leakage of Chemical Products (eg oil, PCB‟s)
Previous or current industrial land use (eg. foundries)
Previous or current agricultural land use (eg. pesticides)
Dumping of industrial and domestic waste (eg Asbestos)
Transfer of waste from neighbouring property (eg seepage)
Outdated building design & materials (eg asbestos)
Length of Exposure
Short-term exposure is called acute exposure. Long-term exposure is
called chronic exposure. Either may cause health effects that are
immediate or health effects that occur days or years later.
Acute exposure is a short contact with a chemical. It may last a few
seconds or a few hours. For example, it might take a few minutes
working in a trench to inhale the fumes of a contaminate.
Chronic exposure is continuous or repeated contact with a toxic
substance over a long period of time (months or years). If a residential
site is contaminated and not cleaned the exposure would be chronic.
Over time, some chemicals, such as PCBs and lead, can build up in
the body and cause long-term health effects.
The extent of Contamination.
Can extend outside of
the site area due to:
List of Contaminative Uses
Iron and Steel works
Oil production and storage
Chemical formulation and manufacture
Dry cleaning industry
Pesticides formulation and manufacture
Waste treatment and storage
Paint formulation and manufacture
Any property containing underground storage tanks
Contaminated Sites in Australia
Western Australia (5,000)
South Australia (4,000)
Northern Australia (5,000)
Figures are approximate and provided by ANZECC
“Should we clean up all contaminated sites to eliminate
impacts or do we remediate only within the constraints
of cost and future land use?”
Identify contaminants or form of
Consider legal and legislative
issues in effect at location
Who is liable and who should
pay the cost of remediation.
Choose a suitable remediation
Remediate the site
Only then, proceed with
Should have the following purposes:
Define the physical site condition
Identify likely contaminants
Quantify the extent and severity of contamination
Assess the effects and constraints on future users
Assess the potential for environmental harm
Assess the hazards to human health of the general public
Assess the hazards to the health of the remediation workers
Assess the best means of remediation
Common Remediation Methods
There are various approaches under this heading:
1. Excavation and Disposal
2. On-site encapsulation
3. Dilution of contamination
4. Clean covers
5. Soil Washing
6. Air Sparging
Other techniques – bioremediation etc
Let’s look at each in detail
1. Excavation and Disposal
Excavate contaminated material, being careful of workers,
dust & run off, then:
Dispose off-site to a licensed tip (dump it!)
This method is being phased out as it does not solve the problem, but transfers
it to another place and another time!
Deliver to licensed decontamination contractor (eg soil wash,
high temperature incinerator, nuclear waste storage, etc)
Used extensively where small amounts of not very serious contaminant are
involved (a few truck loads. eg asbestos)
2. On-site Encapsulation
Encapsulate the offending material, around the perimeter and
over the top (assuming it cannot leach down):
Use water tight slurry walls around the site and a heavy reinforced concrete
slab over the top. Then cover with clean soil and build on slab.
On a large site, may be cheaper than off-site tipping
Requires that encapsulation designs are well founded
A waste treatment license is necessary
Development on the site will be restricted (loads, drainage)
Or (depending on contaminate and future use)
Encapsulation under carpark
The CPWE refers to approximately 45,000 m3 of contaminated sand and coal ash
stored under a car park at the north-eastern end of BIP on Corish Circle,
Banksmeadow. The CPWE was encapsulated in a synthetic liner, Hypalon® in 1980.
The encapsulation was subsequently covered by thick soil walls and asphalt to
establish a car park.
3. Dilution of Contamination
This is used if contamination is uneven or only a thin capping
of contamination overlies clean material:
Example: mix ash contaminant layer with underlying clean clay so contamination is
reduced to within the permitted level, then redistribute mix over the whole site
Advantages: Simple, Cheap, but….
Need quality assurance system to identify unacceptable materials and
prevent their reincorporation into the site
Dilution process could make the contaminants more readily leachable,
thus increasing ground water pollution
If standards change in the long term, site difficult to clean.
4. Clean Cover Technique
The cover consists of a layer of a suitable clean material.
Covers most used (clay; crushed recycled concrete)
Cheap remediation method
Widely used throughout the world
Can not be used to contain gaseous or oily contamination
Used with low hazard level contaminates. Cover depth usually
about half a metre. Must post warnings and advise/restrict sub
contractors who dig.
5. Soil washing
Concept rests on concentrating
contamination in a particular
soil fraction (often in the finer
– Pass soil through various sieves
– Add water or oxidising
chemicals to concentrate
contamination, perhaps enabling
– Concentrate is then taken as
sludge to a hazardous waste tip
6. Air Sparging
Air sparging is the process of injecting air directly into groundwater.
Air sparging remediates groundwater by volatilizing contaminants and
It is akin to blowing bubbles from a straw into a bowl of water. As the bubbles
rise, the contaminants are removed from the groundwater by physical contact
with the air (i.e., stripping) and are carried up into the unsaturated zone (i.e.,
As the contaminants move into the soil, a soil vapor extraction system is
usually used to remove vapors.
The addition of oxygen to contaminated groundwater and soils also enhances
biodegradation of contaminants in and above the water table, as it acts as a
nutrient for bacteria. There are several enhancements to air sparging.
Service station remediation movie clip
Other Innovative Techniques
Some new ideas are now being used, including…
A. Remediation of oily contamination (bioremediation method)
B. Removal of free oil product from water tables (skimming
C. Removal of cyanide and heavier hydrocarbon contamination
(thermal treatment method)
D. Treatment of heavy metal contamination (soil washing
E. Treatment of metal contaminated sites
In more detail….
A. Oil Soaked Ground – Bio remediation
Eight+ different techniques. Most popular is Bio-remediation
Bio-remediation is the natural degradation of organic material to
water and carbon dioxide
Use either natural or specifically tailored micro-organisms: in either case,
nutrients and oxygen are required
Can be carried out in situ, or in mounds of excavated soil
Need to plough up and scarify soil to aerate it and feed bugs
Cheaper, but slower and lower treatment levels than others
Bioremediation – excavation method
In ground method (high water table)
No water table
B. Oil in Water Tables – Simple Removal of free oil near surface
This is encountered on timber treatment sites and coke works
Again, a range of techniques is available, but the most common
one is the Dual Pump System
The deeper pump (in the ground water) creates a “cone of
depression” into which the free floating oil migrates
The skimmer pump, set at the oil/water interface, then
collects the oil (skimming it off the water)
Treatment level is very good but system is not cheap
C. Cyanide Contamination – Thermal treatment
Typical on gasworks or gold mine sites. Remediate by thermal
Excavate, sort and crush (to a 40mm particle size)
Feed soil into rotary kiln thermal units
Preheat soil and move to main heater units for combustion
Cleaned soil is moved to a mixer for cooling and moistening
Flue gases pass thru after-burner with more fuel and oxygen
Finally, clean gases through various dust collectors and filter units to
achieve required emission standards
Treatment levels are good. Inorganic contaminant unaffected.
Main concern is air pollution and relatively expensive
Thermal soil remediation
D. Metal contaminated sites
Typical Approaches :
Soil Washing for heavy metals
Heavy metal pollution can arise from many sources but most commonly
arises from the purification of metals, e.g., the smelting of ores and the
preparation of nuclear fuels.
Electroplating is the primary source of chromium and cadmium. Through
precipitation of their compounds or by ion exchange into soils and muds,
heavy metal pollutants can localize and lay dormant.
Unlike organic pollutants, heavy metals do not decay and thus pose a
different kind of challenge for remediation.
The soil washing method separates the contaminants absorbed in the soil
particles or soil pore by effecting the liquid phase of the soil using water or
A typical soil washing method for heavy metals is divided into two processes:
1) Soil flushing collects the pollutants by letting rinse water circulate in the
2) Soil washing cleanses the excavated pollutants at a Washing Plant. The
basic flow chart of plant washing is shown below. The excavated
contaminated soil is mixed with rinse water and then placed in the
washing equipment. After washing, the soil is separated into fine soil and
coarse-grained soil, which contains the contaminants. The washed soil is
utilized as in-site backfill soil. Meanwhile, the turbid water is dehydrated
at the turbid water treatment plant. The effluent is recycled as washing
water. The dehydrated sewage is then disposed as waste off-site.
Soil washing is comparatively quick
Soil Flushing – generally insitu.
In this method, cement, lime,
thermoplastic and soluble silicate
reagents are used to “fix” the
contamination in low
The stabilisation process involves
excavation, sorting, mixing then
the injection of the reagents
Both soil washing and stabilisation
are effective and fast to
implement, but relatively
Polluter Pays Principle (PPP)
How to determine who should pay?
Division of liability between parties
Exemption from liability
Third party liability
Other liability issues
More on each of these>>
Polluter Pays Principle
“Those who generate pollution and waste should bear the cost
of containment, avoidance or abatement” OECD
Applying PPP simply means that polluter is held liable for
remediation costs and associated costs such as assessment
Australia, as a member of OECD, has accepted the PPP
In practice, applying the PPP is not as easy as theory
How to determine who should pay
Fault-based liability (caused by non hazardous activity)
Risk-based liability (caused by activity with potential risk)
Combination of risk and fault based approaches
Strict liability (caused by hazardous activity)
A general fund (normally industry based)
In practice, it often comes down who is still around and who has
the deep pockets!
Sharing liabilities between parties
This comes into effect if more than one party is liable
Generates considerable litigation
Causes big legal costs that should be used for cleaning up the site rather
than paying lawyers
It slows down remediation
Exemption from liability
„Innocent‟ Land owners and Occupiers
„Lawful‟ polluters: pay for license to pollute!
Third party liability:
Lenders and Financiers, if not “innocent of land use”
There are many types and techniques for remediation of
contaminated sites. It is a technically complex area.
The main objectives for selection are:
Type, volume and degree of disbursement of contaminant
Level of treatment required for intended use of site
Cost involved, versus increased value of clean site
Remediation time: often significant in the development cycle
Determining financial liability is a complicated process. Avoid!
If caught, determine a basis of liability and proceed with in accordance
with legal framework. Don’t broadcast problem!