The district has a legacy of sites that due to their historic use, including former factories, mines, steelworks, and landfills can have a variety of potentially harmful substances such as oils and tars, waste metals, organic compounds, gases and mining materials.

Land contamination can be caused by:

• pollution incidents such as accidents, spills, deposits from the air,
• existing contamination from historical industrial use of the land use (including factories, mines and quarries),
• a contaminant that has migrated overland or by infiltration into the ground,
• high levels of naturally occurring substances such as radon, methane or arsenic,
• historical waste deposits such as a former landfill,
• use of contaminated materials as infill such as demolition wastes.

Land is legally defined as ‘contaminated land’ in the Environmental Protection Act 1990 where substances in, on or under the land are causing or could cause:

• significant harm to people, property or protected species
• significant pollution of surface waters (for example lakes and rivers) or groundwater
• harm to people as a result of radioactivity

The sources of these substances may be their historic use as mentioned above or natural such as radioactivity caused by radon gas.