The historical investigation reopens the history of the site and by so doing uncovers potential reasons for and the type of pollutants. By evaluating and interpreting files, questioning contemporary witnesses or by personal inspection, all environmentally relevant site data is brought together.
But examining the past is not always simple and sometimes only possible to a limited extent. Polluted sites have often been Subject to repeated use (e.g., a petrol station on a former gasworks site), which makes further clarifications more difficult.
For that reason the precision of the (often limited) available data deserves a great deal of attention. The more that is known about a site, the more efficiently the technical investigation can be shaped - to the extent this is not already superfluous. A technical investigation can be superfluous if the clarifications of the historical investigation show that the subsoil pollution is only the result of harmless waste such as brick or concrete debris, or that the site is not polluted with waste at all, in which case it is to be removed from the register.
What is the historical investigation looking for?
- To find out and describe previous activities and uses.
- To identify the environmentally hazardous substances and to localise the area where they were used: Are there places where far higher concentrations of pollutants can be expected (so-called "hot spots")?
- Estimate the amount of the pollutants
- Identify and delimit zones which could be polluted
- Determine whether endangered natural resources might have been affected
- Clarify whether there is a compelling reason to omit a technical investigation
