Ground Gas Assessments

Landowners and developers need to be fully aware of environmental factors and this is initially done through a risk assessment.

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 including:

  • BS 8576:2013 Guidance on investigations for ground gas. Permanent gases and Volatile Organic Compounds (VOCs).
  • BS 8485:2015+A1:2019 – Code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings.
  • BRE 211 – Radon: Guidance on protective measures for new buildings (including supplementary advice for extensions, conversions and refurbishment projects) 2023.
  • CIRIA C665 – Assessing risks posed by hazardous ground gases to buildings (2007).
  • CIRIA C682 – The VOCs Handbook. Investigating, assessing and managing risks from inhalation of VOCs at land affected by contamination (2009).
  • CIRIA C735 – Good practice on the testing and verification of protection systems for buildings against hazardous ground gases (2014).

Monitoring installations will typically be put in place based on the type of site proposed, proximity to gas sources (often landfills), and the strata revealed during the ground investigation. Once the gas monitoring is complete ground-gas protection measures can be designed and put in place such as a ventilated sub-floor and gas resistant membrane.

On some occasions, the concentrations of landfill or soil gas is such that additional measures might be necessary to protect a development. Typical additional measures might include:

  • Vent trenches
  • Venting boreholes
  • Engineered low permeability trenches and layers
  • Search and removal of source areas

Examples of recent GRM news stories related to ground gas assessments can be found via the following links:

To discuss any requirements you might have for Environmental Services, or any other service, please complete the contact form below or call us directly on 01283 551249.

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