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Brownfield land

2012-11-23T13:21:55Z

Kasia: Protected "Development on Brownfield Land": competion ([edit=author] (indefinite))

At the beginning of 1998 the Government announced that at least 60% of new homes are to be built on Brownfield Land by 2008. It followed an earlier announcement stating, that 4.4 million new houses will be required in England by 2016. This means that the total number of houses is projected to rise to around 28 million. As these numbers are significant, the term “Brownfield ‘ can be more often heard in the news and found in the papers, and it is important to clarify the meaning before describing the problems associated with development on Brownfield Land.

The term refers to a land which has been previously developed and might be contaminated. We can distinguish four types of a Brownfield: vacant, derelict, contaminated and partially occupied/utilised. Depending on the level of contamination the preparation of such a land can turn out to be very problematic and expensive. However, because of the shortage of land and the Government law there is a big interest in Brownfield, especially from large developers.

= MAJOR PROBLEMS =

Depending on the character of the previous usage of land (for example factories) different types and levels of contaminations can be found. Depending on the history of the site we can also find different substances in the soil. For example, from former landfills and gasworks both cyanide and phenol can be found. A former waste disposal site would contribute to the significant amounts of cadmium which can be also found in garden soils (especially in the capital). If the source of contamination is down to mineralisation and sewage amendment, then both zinc and copper will be present. Another substance worth mentioning is arsenic in which case the biggest sources are mining and smelting. 

 In more complicated cases the history of the previous industry might not be fully known so it is not certain what chemicals were used. Therefore, before the development even starts, a detailed research is required which of course contributes to the total cost. The tests that have to be conducted are based on taking soil samples at various depths and spots in order to determine both the level of the contamination and its extent. The minimum number of samples required is 9 per ha. The cost of such initial testing can reach even £18,000. This is only the beginning of the spending as more tests and of course clean-up costs need to be taken into account.

The cost and the legal risk (infamous case of drinking water contamination in California commonly known from 'Erin Brokovich' movie) of building on brownfields are therefore the main problems with the government target. Also the city council’s authorities complain that the requirement is too restricting and it limits the number of properties that can be built locally. They argue that control over the development on green belts, which cover 13% of England, should be left to the councils.

= SITE RESTORATION =

If after the initial testing a decision is made to proceed with the development there are three main clean-up techniques to choose from. The first option is excavation and removal of the soil followed by either disposal or off-site treatment. Another approach is to limit the spread of the contamination or choose a treatment to destroy, remove or detoxify containments. Remediation can be divided into two different types which are in-situ (occurs on site on undisturbed soil) and ex-situ remediation (applied to excavated soil either on or off site).

 

{| border="0" cellspacing="0" cellpadding="0" width="500" style="width:500px;"
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TECHNIQUE

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DETAILS

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Soil Removal

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Followed by:
*disposal
*off-site treatment

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Containment

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This option is chosen if other techniques

result in unrealistic costs or create potential hazards

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Soil treatment

(in-situ/ex-situ)

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Contamination can be:
*destroyed
*removed
*detoxified

|}

 

== Soil Treatment ==

There are four main types of treatment options: biological, thermal, immobilisation and washing. The first technique is the most popular one and will be discussed in greater detail.

Biological treatment, also known as bioremediation, is a natural process of cleaning up harmful chemicals. Microorganisms and plants can be used and the treatment is particularly suitable for fuel-based contaminants. This is because microbes "like" to eat chemicals that are found in oil spills (they digest them and produce water and carbon dioxide). For the bacteria to grow the right temperature, nutrients and amount of oxygen must be provided so that it keeps on multiplying (otherwise it will grow too slowly or even die). A way of doing that is to pump in air and add substances (for example molasses). In some countries the cold weather conditions will mean that the soil has to be dug up and cleaned above the ground level with the help of heaters, and while being mixed to provide oxygen.

Bioremediation allows cleaning the soil on site, in some cases even without the need of digging it up. It does not require much labour or equipment and is usually cheaper than other methods - therefore the most common. In other cases, he cost of cleaning up a tonne of soil in UK is between £5 and £12. This depends on several factors such as the type and level of contamination and the size of land. On top of that, the excavation costs of about £2.5 per tonne have to be covered.

 

= AFFORDABILITY =

Although some solutions are cheaper than the others the cost of the site investigation and soil treatment is still significant. This is why building on the contamination land can have an effect on the future houses/flat/rent prices. Construction companies therefore point out to the government that it should cover the cost of cleaning up the land. Otherwise, providing affordable houses build on brownfields will not be possible.

Brownfield land

2012-11-23T13:20:16Z

Kasia: Created page with " At the beginning of 1998 the Government announced that at least 60% of new homes are to be built on Brownfield Land by 2008. It followed an earlier announcement stating, that 4...."

User:Kasia

2012-11-23T11:33:58Z

Kasia: Created page with " {| border="1" cellspacing="1" cellpadding="1" style="width: 500px;" |- | NAME | Katarzyna Piontas |- | OCCUPATION | Student |- | ORGANISATION | University of Leeds |- | COUR..."

{| border="1" cellspacing="1" cellpadding="1" style="width: 500px;"
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| NAME
| Katarzyna Piontas
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| OCCUPATION
| Student
|-
| ORGANISATION
| University of Leeds
|-
| COURSE NAME
| Civil Engineering with Construction Management
|}

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