Typical for chlorinated solvent pollution in the soil is the heterogeneous pattern. Pollution is spread unevenly over the soil matrix, making it very difficult to detect and characterize the source zones, especially in an urban environment. Considering soil sampling for chlorinated solvents, the difficulty is to avoid the volatilisation of the (very volatile) solvents during the sampling process. A few innovative techniques have been developed but at this point it is not clear which technique would produce the best result in a certain situation. CityChlor will test certain techniques.