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Site Contamination

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					Site Contamination
           Land Contamination
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:


             •Slope
             •Rain/Runoff
             •Transport
             •Wind
             •Ground water
                                List of Contaminative Uses

   Mining
   Iron and Steel works
   Gas works
   Oil production and storage
   Chemical formulation and manufacture
   Explosives industry
   Dry cleaning industry
   Pesticides formulation and manufacture
   Metal treatment
   Waste treatment and storage
   Service Stations
   Paint formulation and manufacture
   Photographic developers
   Any property containing underground storage tanks
                       Contaminated Sites in Australia
   Victoria (20,000)
   NSW (7,000)
   Queensland (6,000)
   Western Australia (5,000)
   South Australia (4,000)
   Northern Australia (5,000)
   Tasmania (1,000)
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?”
                                       General Approach

   Investigate site
   Identify contaminants or form of
    contamination
   Consider legal and legislative
    issues in effect at location
   Who is liable and who should
    pay the cost of remediation.
   Choose a suitable remediation
    technique
   Remediate the site
   Only then, proceed with
    development
                                      Site Investigation

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
material)

 –   Pass soil through various sieves
 –   Add water or oxidising
     chemicals to concentrate
     contamination, perhaps enabling
     settlement.
 –   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
    enhancing biodegradation.
   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.,
    soil).
   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
     method)
C.   Removal of cyanide and heavier hydrocarbon contamination
     (thermal treatment method)
D.   Treatment of heavy metal contamination (soil washing
     method)
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
                                                           Water
                                                           Table


                                   Soil
   dual pump
diagrammatic
         C. Cyanide Contamination – Thermal treatment

Typical on gasworks or gold mine sites. Remediate by thermal
  techniques

   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
Rotary kiln
D. Metal contaminated sites

Typical Approaches :

   Soil washing
   Soil flushing
   Stabilisation
   Magnetic
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
    agents.
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
   ground.

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
 Typical
    Soil
Washing
Soil Flushing – generally insitu.
                                        Stabilisation

In this method, cement, lime,
   thermoplastic and soluble silicate
   reagents are used to “fix” the
   contamination in low
   permeability soils
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
   expensive
Magnetic
                                    Financial Liability

Some principles:
 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
  and auditing

   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”
                                                       Conclusion

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!
END

				
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