Ground gas
The term ‘ground gas’ refers to gases such as carbon dioxide and methane, which are generated within the ground and/or within landfills, commonly from the breakdown of vegetative matter. Ref The HS2 London-West Midlands Environmental Statement, Glossary of terms and list of abbreviations, DETR 2013.
Approved document C, Site preparation and resistance to contaminants and moisture, suggests that ‘methane and other gases’ includes hazardous soil gases (other than radon, which is dealt with separately), which originate from waste deposited in landfill or are generated naturally.
They may include gases such as methane, carbon dioxide, volatile organic compounds (VOCs) and nitrogen which can migrate through the subsoil and through cracks and fissures into buildings, where if they build up to hazardous levels, cause harm to health or compromise safety:
- Methane is an explosive and asphyxiating gas.
- Carbon dioxide is toxic.
- VOCs are flammable and toxic and can have an unpleasant odour.
They may be apparent as:
- Landfill gas, produced by the action of micro-organisms on biodegradable waste materials, including; methane, carbon dioxide and small quantities of VOCs.
- Elevated levels of carbon dioxide and nitrogen, occurring naturally in coal-mining areas
- Methane and carbon dioxide occurring in organic rich soils and sediments such as peat and river silts.
- VOCs occurring as a result of petrol, oil or solvent spillages.
The assessment of the risk from ground gases should adopt a tiered approach. A preliminary risk assessment should be undertaken, and depending on the outcome, either a generic quantitative risk assessment (GQRA) or detailed quantitative risk assessment (DQRA), or both, may be necessary.
Where risks are unacceptable then these need to be managed through appropriate building remedial measures or site-wide gas control measures, such as the removal of the gas generating material or 'covering' (placing one or more layers of materials over the site) together and the use of gas extraction systems.
Control measures for dwellings may include gas resistant barriers above an extraction or ventilation layer from which gases can be passively dispersed and vented to the atmosphere.
Control measures for non-domestic buildings, which may have a larger footprint, may require mechanical dispersal and ventilation systems, monitoring and alarms. These systems will require ongoing maintenance and calibration.
[edit] Related articles on Designing Buildings
- Brownfield land.
- Building on fill.
- Contaminated land.
- Cover systems for land regeneration - thickness of cover systems for contaminated land (BR465).
- Deleterious materials.
- Designing to reduce the chemical, biological and radiological vulnerability of new buildings (IP 7/15).
- Ground conditions.
- Landfill tax.
- Methane.
- Natural gas.
- Pollution.
- Pre construction information.
- Radon.
- Radon: Guidance on protective measures for new buildings BR 211.
- Radon protection for new domestic extensions and conservatories with solid concrete ground floors (GG 73 revised).
- Radon protection for new large buildings GG 75.
- Radon protection for new dwellings GG 74.
- Radon solutions in older homes GR 38.
- Site appraisal.
- Site information.
- Solid and liquid contaminants risk assessments.
- Synthetic methane.
Featured articles and news
Introducing or next Guest Editor Arun Baybars
Practising architect and design panel review member.
Quick summary by size, shape, test, material, use or bonding.
Types of rapidly renewable content
From forestry to agricultural crops and their by-products.
Terraced houses and the public realm
The discernible difference between the public realm of detached housing and of terraced housing.
Put digitalisation and sustainability at the core of curricula
Project management educators are urged.
Looking back at the influence of climate events
From a designer and writer: 'There are limits to growth but no limits to development'.
Terms, histories, theories and practice.
Biophilic design and natural light
Letting in the light and natural elements into spaces.
APM Programme Management Conference 2024
Strategies for Success.
Residential takes the reins as contract awards even out
Contracts down, but remain above the last quarter of 2023.
Celebrating Eid and the largest mud-brick building.
Barry Kingscote claims prestigious CIOB CMYA Award.
The British Mosque: an architectural and social history
The story of some 1,500 mosques or more in Britain.
Heat pump refrigerants, efficiencies and impacts
R12 to R1270 what are the differences?
Global heat pump market in 2023
Challenging times with positive but modest outlook.
Beyond the infrastructure pipeline
Opportunities and chokepoints.