Soil gas surveying is a method gaining in popularity for groundwater chlorinated solvent pollution studies, particularly in the USA. Previously published methods have advocated on-site analysis; this study presents a simple method where samples are transported to a laboratory for analysis, hence minimizing the need for specialized field analytical equipment and trained field personnel. Tests show the method provides reliable results, comparable with those of established on-site analysis methods. The soil gas surveying method has been applied to a contaminated industrial site where it was successful in defining an area of significant chlorinated solvent pollution. Preliminary analyses from investigation boreholes indicate that this area has severe groundwater pollution.

This paper provides a method of identifying land contaminated with chlorinated hydrocarbon solvents by sampling and analysing soil gas. Relationships are presented which enable levels of soil gas contamination to be related to levels of soil and groundwater pollution. Two case studies are presented. Soil gas surveying of an industrial site with severe groundwater pollution demonstrated that standards for contaminated land are insufficient to protect groundwater. Solvent levels in groundwater were one to two orders of magnitude higher than UK permitted concentrations in drinking water, whereas soil contamination values did not reach polluted levels. Surveying of a site occupied by a disused fire station showed significant differences in patterns of soil gas and groundwater pollution. This is explained by direct pollution of groundwater though the well at the site and/or possible flow of polluted groundwater to the site from adjacent areas.