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Determining Site Contaminants

Contaminants - Outline
A building site may contain hazards that are naturally occurring or the result of some previous use of the site. Examples of such contaminants are: radon, carbon dioxide, methane, sulphates, acids or chlorides.

Housing and risk areas
An area that is high-radon is where the Radiological Protection Institute of Ireland (RPII) survey shows more >10% of houses are likely to have radon level in excess of the National Reference Level (200 Bq/m3).
A low-radon area is one where <10% of houses exceed 200 Bq/m3.

Radon is a radioactive gas that is naturally occurring. Radon seeps up from the ground and can build up to unacceptably high concentrations in buildings. Exposure to radon over a period can lead to lung cancer. Additional information is available from:
  • The Environmental Information Service (ENFO),
     17, St. Andrew's Street,
     Dublin 2
  • The Radiological Protection Institute of Ireland,
     3, Clonskeagh Square,
     Dublin 14
  • Environmental Protection Agency (EPA),
     PO Box 3000,
     Johnstown Castle Est.,
     Co. Wexford
  • British Research Establishment (BRE)
  • Report BR211: 2007 Radon: Guidance on Protective Measures for new Dwellings (including supplementary advice for extensions, conversions and refurbishment)
  • “Building on Derelict Land” by B. A. Leach and H. K. Goodger. CIRIA/PSA publication, ref: SP78, 1991.
  •; › Guidance › Topics › Radiation › Ionising radiation;

Methane and Carbon Dioxide
The last few years have seen an increase in the number of incidents involving landfill gas in buildings. The main components of landfill gas are carbon dioxide (toxic) and methane (flammable). If either gas enters a building it can pose a risk to health and safety. These two gases are not just associated with landfill; they are also associated with sewage, coal strata, river silt and peat. A site investigation should be undertaken by a specialist if there is a risk of carbon dioxide or methane.
Further information may be attained from: 
The British Research Establishment (BRE) Report BR 212:1991 “Construction of new buildings on gas-contaminated land” available from: 

Landfills and Chlorides
For guidance on appropriate measures to be taken when designing a building on or near sites containing landfill, consult the Department of the Environment publication, “Protection of New Building and Occupants from Landfill Gas”, available from:
Government Publications, 
 St., Dublin 2; 
 Tel: 01 6613111

The presence of chlorides increase the risk of a chemical attack on the concrete and of corrosion to reinforcement. A suitably qualified consulting engineer who is qualified by examination, in private practice and possess professional indemnity insurance should be appointed to design the concrete mix specification and reinforcement details.

Acids and Sulphates
In filled sites, sulphates are known to cause expansion and disruption of concrete. A suitably qualified consulting engineer should be employed to specify a concrete mix specification which takes account of the risk.
Guidance is presented in BRE Special Digest 1 “Concrete in aggressive ground”.

In peaty soil and other soils, there can be a high acid content which can result in damage of concrete. The following precautions may be necessary to avoid such damage:
  1. Thorough compaction over all the foundations.
  2. Use of special cements.
  3. Use a protective layer, like bituminous or plastic membrane to stop the contaminants and concrete coming into contact with each other.
  4. Increase cement concentration in the aggregate mix
To avoid costly repairs, again it is essential to seek the advice of a suitably qualified person.

Sites likely to contain contaminants
Sites where the following works have taken place are likely to be contaminated:
Sites which were formerly used for:
  • Chemical works
  • Asbestos works
  • Industries making or using wood preservatives
  • Gas works, coal carbonisation plants and ancillary by-product works
  • Waste disposal sites and Landfill or ground within 250 metres of such sites
  • Metal mines, foundries, smelters, steel works and metal finishing works
  • Oil distribution and storage sites
  • Paper and printing works
  • Railway land, especially the larger sidings and depots
  • Sewage works, sewage farms and sludge disposal sites
  • Scrap yards
  • Tanneries

Contamination signs from previous site-use
On some sites investigation of contamination arising from a previous use of the site may be necessary. The following lists give some guidance for recognising such risks and potential contaminants. Further guidance is set out in BS 10175: 2011 Investigation of potentially contaminated sites. 
This standard is available from

Identifying Contaminants – Signs
Below are some areas where inconsistencies or abnormalities may be possible signs of contamination:
  • Vegetation (absence, unnatural or poor growth)
  • Surface materials (unusual contours and colours may indicate residues and wastes)
  • Odours and fumes (may indicate organic chemicals at very low concentrations)
  • Containers or drums (whether empty or full)

Possible Contaminants
Some possible contaminants have been listed below, please note this is not an exhaustive list:
  • Metal compounds, metals, organic compounds, gases 
This is generally gives rise to poor vegetation growth
  • Metal compounds, metals, oily and tarry wastes, other fibres, asbestos (loose), organic compounds (containing phenols), potentially combustible material including coal and coke dust, waste and refuse.
This is generally gives rise to unusual colours and contours on the soil or site.
  • Explosive, flammable and asphyxiating gases including methane and carbon dioxide, faecal, corrosive liquids, animal and vegetable matter (biologically active).
This is generally indicated by fumes or odours on site.
  •  Containers or drums (empty or full)
Indicative signs are any of the above.
Foundations Radon Insurance Professional indemnity