Soil samples are collected around sites where materials may have been spilt, where storage tanks may leak onto or into the ground, and where aerial emissions may deposit contaminants around a site.
These samples are analysed for particular contaminants, to determine whether there could be a risk to the environment (including human health if people live on or use the land). The Council also collects soil samples from a number of farms in the region, to monitor the ongoing effects of agriculture on soil health and soil properties.
Soil samples may be collected from just the surface layer (the zone of most interest if people or animals live on the land), or from a soil profile extending down 50 cm or more (to monitor the movement of contaminants such as metals down into groundwater).
Information about the average quality of soil across a property or site is normally of more interest and relevance than information about the soil at just one spot, and so usually a number of soil samples at different points are collected and combined before analysis.