What Is A Ground Gas Risk Assessment?

The aim of a Ground Gas Risk Assessment is to identify and quantify ground gas risk to specified receptors.

Ground Gas Risk Assessments are often required as part of planning conditions on a development site and successful completion and sign-off the project is unable to be completed until mitigation or remedial works identified, have been executed.

Ground Gas Risk Assessments monitor for the presence of both natural and anthropogenic gas sources including methane, carbon dioxide, carbon monoxide and hydrogen sulphide.

When Do I Need Ground Gas Risk Assessment?

A Ground Gas Risk Assessment will be identified within the Phase 1 Desk Study. If the site is considered at risk as a result of this investigation, a Ground Gas Risk Assessment will be recommended.

Factors which can make the requirement for a Ground Gas Risk Assessment more likely can include proximity to landfill sites (current or historical), historic land use (particularly heavy industrial), infilled ponds, lakes or water sources as well as natural sources.

Ground Gas, whether derived from landfill, mining or natural sources can pose a serious threat to a development. If there is a viable linkage through the ground that allows these gases to migrate into buildings, it can allow for an accumulation of gas in confined spaces. This can cause a serious threat to health in some situations or even asphyxia following elevated concentrations of gasses in confined spaces. This has most commonly been seen in mining accidents.

Did you Know?

Ground Gas levels can be very sensitive to adverse weather conditions. Therefore, it is very important that monitoring is undertaken during periods of rising and falling of atmospheric pressures. This will therefore allow for assessment of the worst-case scenario.

What Are The Sources of Ground Gas?

There are a numerous sources of ground related gases, this can include:

  • Landfill sites
  • Made Ground
  • Foundry Sand
  • Sewage Sludge
  • Infilled Ground
  • Spills/Leaks/Discharges
  • Mine Workings
  • Peat Bogs
  • Organic Rich Alluvial Deposits
  • Radon and Carbonate Rich Strata

What Remedial Options are Available?

Should the Ground Gas Assessment indicate that a development is at risk from ground gases, mitigation methods can be proposed within the development design to reduce these risks to an acceptable level.

These can include:

  • Manage (remove, modify) the original source
  • Interrupt the pathway
  • Modify the receptor or the behaviour of the receptor

How EMS Geotech Can Help

EMS Geotech provide cost effective risk assessments and ensuing remedial recommendations for your development.

Our qualified Geo-Environmental consultants have experience and expertise relating to gas monitoring, qualitative and quantitative risk assessment and supervision and validation of installation. This will ensure the requirements of the project are satisfied.


ground gas monitoring