A Practical Approach for Site Investigation - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 158

So in addition to reporting factual information obtained in the Exploratory
Investigation, the report on the Exploratory Investigation also has to discuss the
hypotheses that were on the basis of the investigation and define if the obtained
results confirm or deny them.
Finally, the question if a Main Investigation is necessary has to be answered
during the Exploratory Investigation. Obviously, when no contamination was found
and this conclusion is in line with the hypothesis (uncontaminated site), there is
no need for conducting a Main Investigation. This can be the case, for example,
when the location of an underground storage tank has been well established dur-
ing the Exploratory Investigation, but when no contamination has been found. The
obvious conclusion is that there is no contamination originating from the tank and
consequently the results of the Exploratory Investigation are sufficient to end the
investigation of the site.
But even if the hypothesis has proved to be incorrect, the need for a Main
Investigation might be absent, for example when the concentrations found are
enhanced in comparison to local background values and/or Soil Quality Standards,
but still are relatively low so that there is no apparent need for further actions. In
this case we also have to be careful that accidentally the samples in the Exploratory
Investigation were taken on the boundary of the contamination and not in the centre,
thus implying lower concentrations than are actually present on the site.
Finally, no additional investigation might be necessary when the objective of the
Exploratory Investigation did not originate primarily from an environmental per-
spective, such as for example when it was performed in relation to the decision
whether to buy a site.
In all other situations, thus where the contamination was actually found (in
sufficiently high concentrations), there will be a need for a Main Investigation.
3.8 Main Investigation
The goal of the Main Investigation is to provide the necessary information to deal
with the contamination, the presence of which was confirmed during the Exploratory
Investigation. What level of information is necessary, both for the contamination
as well as for the site characteristics, will depend on a variety of site specific
parameters, but the aim is to perform a cost-effective investigation.
The Main Investigation should be the final investigation phase prior to manage-
ment actions (e.g. remediation). That implies that, apart from obtaining a more
detailed view of the spatial distribution, the Main Investigation should also pro-
vide information that can be used to determine the urgency of a remediation, in
regard to the present or future land-use, as well as information that is essential for
the application of remedial actions. Consequently, the Main Investigation should
not only focus on the contamination, but should also take account of quite dif-
ferent factors, like the identification of potential exposure pathways. When there
is clarity on potential remediation measures, the Main Investigation should take