Sniffing out contamination

AFHA was commissioned to assess this contamination and make recommendation on appropriate construction materials and methods. Using a portable photo-ionisation detection (PID) system, excavations and samples collected during geotechnical investigation, were 'sniffed' for presence of volatile organic compounds, such as petroleum hydrocarbons. This screening assisted selection of samples and decisions on analytical requirements for chemically characterising the samples.

Assessing Risks - making decisions

Using the PID on-site testing equipment, and more detailed laboratory tests, Howland's were able to advise on specific risks to human health posed by vaporous organic compounds and on necessary steps required to prevent human exposure to them.

Localised pockets of contaminated soils are likely to be encountered during tunnelling, and these will be sampled and tested for general organic contaminant indicators which will be correlated with more detailed analyses carried out previously. The worst case scenario is assumed where these are encountered, and full personal protection equipment is encouraged to ensure worker health and safety. Also, advanced tunnel ventilation systems will be constructed to maintain sufficient circulation of fresh air and minimise accumulation of potentially asphyxiating gases in confined spaces.

Discussions with the Environment Agency and local authorities continue to ensure all impacts of the scheme on the groundwater regime are adequately addressed. Our continual on-site presence maintains quality engineering methodologies and client confidence.