If contamination is suspected on a piece of land, soil samples are taken (using either hand held equipment like trowels and hand augers, or mechanical equipment which can take deep cores of soil) and analysed at a scientific laboratory for contaminants. Most soils will contain small amounts of common urban contaminants such as heavy metals and hydrocarbons and it is the concentration of certain contaminants that determines if the soil is a risk to human health. DEFRA and the Environment Agency have set guideline values for some contaminants which show the concentrations within soil at which there is a minimal risk to health. For more information visit the Environment Agency website.
When is land officially 'contaminated'?
Just because a source of pollution may exist (for example, petrol that may have leaked from an underground storage tank), it does not mean that the land is necessarily classified as contaminated. To be classed as ‘contaminated’ there must be a way for the pollution to reach a person, or water course. The route from the pollution to a person is known as a pathway, and a person or water course is known as a receptor. If there is no pathway, or receptor, then the land cannot be called contaminated. This is known as the source-pathway-receptor relationship.
If these three don't already exist, they need to be considered when a site is redeveloped in case the works that happen create these where they didn’t exist before. A site must always be suitable for its current or intended use.