Gas protection is a technical solution to prevent or to control gas penetration into properties. The control of gas migration is normally achieved by blocking the pathway or removing the source of the gas generation. There are several methods available to achieve the protection of existing / new build properties and also another factor is the use of the property and size (economic factors).
The main components that developer have to be aware of in the U.K are methane (which is flammable at 5% to 15% by volume in air) and carbon dioxide (which is toxic), after two gas explosions in the U.K. in the 1980s Loscoe and Abbeystead. Building Research Establishment, British Standards, the Department of Environment and other regulatory bodies including ones in construction industry developed and published guidance for preventing gas ingress into building of these two gases in the UK. Their production in the environment are associated with coal seams, deposited river silt, sewage, landfill, and peat.
In the case of landfill gas migration, the gas is produced by the organic materials in the waste degrading over time. Creating varying concentration over time (CO2 typically 40% by volume and methane (CH
4) typically 60% by volume), as previously explained this gas can be heaver than air or lighter depending on the concentrations of these gases and air, but will move from an area of high pressure to one at a lower pressure irrespective of its relative density.
To try to prevent landfill gas migration from the site the operator should employ such methods as leachate drains with venting, low permeability geomembranes, slurry trenches, and grout curtains around the landfill site.
Read more about Gas Protection: New Buildings On Contaminated Land, Building Near Landfill Sites, Integrity Testing
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