Gas sweep surveys
Whether it's an internal gas sweep or external surface emissions survey, this family of techniques are useful tools in monitoring and assessing ground gas risk.
Read on to find out more.
Talk a walk with our colleague, Emily, out doing a gas sweep survey to inform the best location for a flux box test
What is a gas sweep survey?
Gas sweep surveys are a family of techniques we can use to add an extra spatial dimension to a ground gas investigation.
Using high resolution single gas instruments, these survey techniques allow us to detect small changes in gas concentrations immediately above the ground surface. This includes gases such as methane and carbon dioxide.
This helps us to identify any ground gas migration pathways - from discrete point source features to diffuse areas of gas emissions.
These survey techniques are useful both indoors (internal gas sweeps), and externally (surface emissions survey).
Why are they useful?
We use internal gas sweep surveys inside residential or commercial buildings, to identify points of likely ground gas ingress into a property. Commonly, this includes defects in the building fabric or utility service entry points, or even plumbing systems. These surveys help us provide ground gas risk assessment for existing or newly built properties.
We use external emissions surveys to locate 'hot spots' of increased emissions of ground gas through the surface of an external site. We use these surveys for a range of purposes including monitoring emissions from landfills and providing risk assessment for potential re-development sites.
Sweep surveys are also very useful in helping inform other elements of our ground gas investigation monitoring strategy. For example, carrying out an initial sweep survey can help us select the best location for a flux box test or continuous monitoring instrument deployment.
Benefits to your project
Key benefits that gas sweep surveys bring include:
adding an additional spatial line of evidence to your ground gas investigation
when used over large areas, geo-referencing of surveys enables sophisticated GIS analysis
a relatively quick, simple and inexpensive gas survey techniques
helping to more accurately tailor monitoring programmes to target areas of high gas emissions.
Want to know more? Then feel free to get in touch.