Ground gas risk: Providing independent assurance for developments

When constructing new developments, local planning authorities, warranty providers and future house purchasers need independent assurance that the development is safe from any ground-gas risks. With a detailed knowledge of ground gas, gas protection measures and the construction process, RSK Geosciences has developed a range of independent services for integrity testing and gas protection system verification.

“As an independent gas-protection-system verifier, RSK Geosciences has a nationwide team of specially trained, experienced and competent geoenvironmental engineers to carry out our specialist services across the UK,” explains Chris Larkin, RSK Senior Geoenvironmental Engineer. “Clients, installers and regulators can call upon us for a wide range of independent gas protection system and gas membrane integrity testing verification services.”

Independent verification of gas protection systems is essential for regulators to sign off conditions relating to their sites and to ensure the protection of human health from potential ground gases that can cause intoxication, asphyxiation or explosions. It also avoids potential or perceived conflicts of interest with appointed membrane manufacturers, installers, designers and consultants.

“Here at RSK Geosciences we offer a full suite of services, from visual and mechanical inspection through to air-lance testing and dielectric testing,” explains Chris. “For low-gas-risk sites, where the installers are confirmed to be suitably competent, our engineers can carry out visual inspections to examine membrane integrity, service entrances, and corner and air brick detailing. This may need to be supported by a mechanical test, where we will look for unbonded seams and joins between sheets of membrane, or around service entrances, corner detailing and air brick detailing using a blunt pointed instrument.

“For higher-risk sites, air-lance testing and dielectric (electronic leak detection) tests may be recommended, which enable our engineers to rapidly test larger areas and quickly locate defects in membrane integrity,” says Chris. “Air-lance testing involves using an air compressor and bespoke wand to force 50 PSI of air pressure through a 4 mm nozzle along seams, joins and welds, while dielectric testing sends a high voltage direct current to the surface of the membrane via a phosphor-bronze brush. Even a pinhole triggers an alarm by earthing to the underside of the membrane.

Air-lance testing

Dielectric testing

“All our gas membrane verification services are carried out in accordance with CIRIA C735 guidance and are determined following a review of the site gas regime, installer competencies, materials used, the methodology of installation, and the wider construction process.”

For more information on RSK Geosciences’ gas protection and verification services please visit the webpage or contact Chris Larkin.