Ground Gas Membrane Testing, Inspection, Verification and Validation

Understanding Ground Gases

Ground gases occur in the soils and rocks at surface and subsurface levels. These gases can occur both naturally e.g., methane, nitrogen and radon, and as a by-product of human activity e.g., carbon dioxide, carbon monoxide, and methane.

The impact of ground gases on development projects has become increasingly important in recent years primarily because of the need to build on brownfield sites. By definition, brownfield sites have previously been developed and used, and may therefore contain landfill, contaminants, and other industrial waste liable to produce ground gases.

The Risk of Ground Gases on Developments

Ground gases can exist in the soil and rocks on which developments are constructed. If ground gas protection is not put in place, then these gases could enter buildings through various channels including wall cavities, service pipe workings, and breaks in construction materials. They can readily accumulate in enclosed areas around and within the building, potentially causing harm to occupants via inhalation or explosion.

Legislation has therefore been introduced that requires developers to assess the risk of ground gases, take protective measures, and have these measures independently inspected and verified to ensure gas membrane requirements have been met.

What Does Verification Involve?

The scope of the verification will depend on the competency of the installer, complexity of the gas membrane design and severity of the risk from ground gases.

As part of our gas membrane inspection service, GRM will undertake visual checks to look for defects and punctures, and a manual ‘pick’ test to check seals along seams and joints and around service entries.

We can also provide air lancing and other gas membrane integrity testing services as required.

The verification is necessary to demonstrate that the gas protection systems have been installed correctly, in accordance with the design, and can be relied upon to provide the required level of protection.