2. A difficult diagnosis

The most problematic aspect of soil and groundwater pollution is the identification and characterization of pollution. This essential preliminary step comes up against :

• the almost invisible nature of the sources and their effects;

• the cost of reconnaissance techniques ;

• to the heterogeneity of the environment under consideration.

In order to avoid a systematic and costly search for soil pollution, through regular sampling, it is generally preferable to rely on in-depth historical research into activities and incidents that may have occurred on the site, before defining targeted physical reconnaissance programs. The shortcomings of memory and archiving are offset by a cautious, rigorous and rather safe approach to the investigation and interpretation...