A recent BBC news article highlighted the importance of supposed ‘green field’ sites benefiting from contaminated land investigations. The article refers to a proposed housing development at Hampton Lovett, Worcestershire. The plans for almost 200 new homes have caused anthrax concern: ‘Worcestershire Regulatory Services is worried livestock carrying the infection [anthrax] may have been buried there’.[1]

Anthrax is a bacterial infection caused by bacillus anthracis. It is spread by contact with the spores of the bacteria which are often from infectious animal products. The spores can survive in harsh conditions for decades or even centuries. Such spores can be found on all continents, including Antarctica. The spore can lay dormant in soil for many years, so there are health & safety implications if animal remains are found on the site. Disturbed grave sites of animals have been known to cause infection after 70 years.

Common sources of contamination affecting Green-Field Sites can include:

• Piggeries

• Nearby historical landfills

• Small demolished buildings such as animal shelters

• Historical Quarries

• Agricultural Usage

Conducting thorough contaminated land investigations of a site prior to its planned usage is paramount, in many cases planning permission is dependent on it. There are several stages involved in a contaminated land investigation, dependent on the result of each stage.

Phase 1: Desk Study

The first stage of land investigations are qualitative investigations, or phase 1 desk study. Investigations begin by looking at historical maps of the site and area and gathering environmental information. This type of information includes the former uses of the site. Sites of interest would include former uses as historical landfills, factories, industrial land, manufacturing depots and animal sites such as piggeries.

Geological information and hydrological information, such as water courses and the type of aquifer (groundwater source) present will also be reviewed.

An initial site inspection is made to visually evaluate the site then a risk assessment will be produced. This will consider:

• Sources of contamination

• Pathways (contamination transfer)

• Receptors (including current and future users of the site, plants, groundwater and surface water

Sources of contamination which can be present on green field sites can include historical pesticide usage (such as lead and arsenic found in dusting powders used in orchards), animal burials and backfilled ponds. Clay pits and quarries can also be a source as these can often host a variety of contaminants including asbestos and potentially be a source of ground gas. Ground gases include methane and carbon dioxide. These gases primarily come from landfill or historical landfill sites.

Once this process is complete a conceptual site model is produced which indicates a risk for each receptor from the contamination sources identified at the site. Depending on the levels of risk identified, further investigations may need to be undertaken.

However, for many green field sites the desk study report will conclude that very little risk exists and no further work is required.

Phase 2: Ground Investigations

If the site needs further ground investigations the investigation moves on to phase 2 ground investigations. This stage is to quantify the risks identified in phase 1.

Machine excavated trial pits are usually undertaken.  Soil samples are taken from these trial pits and sent to an external laboratory for contamination testing.  The results of the contamination testing are then evaluated and the conceptual site model is revised.

On many sites the contamination testing will find that no unacceptable contamination risks exist and that no further work is required.

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Phase 3: Remediation

If Phase 2 finds unacceptable risks from contamination remediation is usually required.  This can include:

• Soil Cover Layers for soil contamination

• Gas proof membranes for ground gas

• Complete excavation of the contaminated soil