Vapour Intrusion

Land that has been contaminated with solvents and petroleum hydrocarbons such as trichloroethylene (TCE), benzene, or toluene, including landfill gas (such as methane and hydrogen sulphide) can lead to hazardous vapours entering a building.

Depending on site and building specific conditions, vapours can accumulate inside the building to levels that cause a risk to human health.

To eliminate risks, passive building mitigation measures are usually implemented such as sealing openings, installing vapour barriers or a venting layer. In extreme circumstances, active systems may be required such as a sub-slab depressurisation system.

As it can take several years, or even decades to clean up contaminated soils and groundwater, protective measures will be needed until it can be scientifically proven that vapour intrusion no longer poses a risk to a building’s inhabitants.

Key T+T vapour intrusion projects:

  • Development of a supermarket impacted by a chlorinated solvent plume
  • Development of a supermarket on a former aerosol manufacturing plant
  • Development of land occupied by the former bulk fuel farms at Wynyard Quarter
  • Investigation of a chlorinated solvent groundwater plume from a dry-cleaning site

T+T capabilities in this field are:

  • Detailed subsurface soil and groundwater investigations and plume delineation
  • Soil gas measurements
  • Indoor air sampling and measurements
  • Vapour intrusion modelling using RISC, RBCA and USEPA J&E model
  • Risk characterisation and assessment
  • Remedial design of vapour barriers, sub-slab depressurisation, venting and treatment systems
  • Vent dispersion modelling
  • Compliance monitoring