Ground Gas Membrane Testing, Inspection, Verification and Validation

Ground gases can be produced from a variety of natural sources including coal, peat, alluvial deposits and rock (Radon), plus a range of man-made sources such as landfills, in-filled ponds, made ground and spillages of fuel and volatile organic compounds (VOCs).

GRM provides risk assessments to identify and quantify ground-gas risks to specified receptors based on current guidance and regulations.

What are 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.

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How Can Ground Gasses Affect 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.

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Why is Verification Required?

Where risks from ground gases such as radon, methane or carbon dioxide have been identified, independent gas membrane verification is necessary to ensure and demonstrate that the ground gas protection measures have been adequately installed.

Even when a qualified installer is used, the various regulatory bodies and current guidance (BS8485:2015+A1:2019) require that these membrane installations are also validated by a third party. GRM offer ground gas membrane protection validation in line with CIRIA C735 (Good practice on gas membrane testing and verification of protection systems for buildings against hazardous ground gases – guidance on expected frequency for verification).

Our ground gas protection verification service is 100% independent of the membrane manufacturer, installer and client.

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.

Why work with GRM?

GRM is one of the founding members of the British Verification Council (BVC) and has been undertaking gas membrane validations for over 15 years.

We have a dedicated team of experienced inspectors who have all attended external training courses including the CL:AIRE Verification of Gas Protection Systems, in addition to practical on-site training. Our GRM team work across the UK on both residential and commercial developments and can often attend at short notice.

The team is led by Siobhan Jackson, a Chartered Environmental Scientist with over 20 years’ experience in the land contamination industry.

If not already available, we can also provide a Gas Protection Measures Design and Verification Plan and undertake regulator liaison on your behalf to agree the scope of any gas protection measures and the subsequent validation programme.

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