Land quality

Extensions - risk from ground gas

Hounslow has a long history of industrial activity and landfilling. This has sometimes caused contamination of land or created areas where landfill gas is released. These pose a hazard when the land is redeveloped and can be identified by property searches when land is bought or sold causing sales to fall through.

Small developments such as extensions may not require planning permission. This means that we are unable to require builders or land owners to undertake testing or install precautionary measures, as they would for a larger development.

This could lead to owners and occupiers being exposed to health risks or being unable to demonstrate the safety of the site, for example if they wish to sell it. Site workers could also be put at risk.

Anyone responsible for small developments and extensions should take documented steps to ensure that there is not a risk from contamination or ground gas.

The risks could be:

  • contamination of the soil by former activities
  • contamination of water under the site, for example by from fuel leaks or disposal of used oil or solvents
  • ground gas entry into the building

Contamination of the soil or water is not always possible to see without chemical testing. However, there are signs that can indicate that a problem is more likely to be present, for example an oily appearance, chemical smell, or the presence of waste or material different from the normal soils in the area. If you identify any of these please contact the land quality team by emailing us or calling 020 8583 5555.

We have created a tool to allow developers to identify when developments are in an area where ground gas protection measures are normally required by our planners. Please note that there are separate requirements under building control regulations which may cover a wider area than is covered by this tools postcode search.

Enter a postcode where the building works are taking place:

  • If it indicates that there is a risk from ground gas then contact the land quality team
  • If your building is in the search zone then you should contact the landfill team

Identify if a property is at risk from ground gas

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