Environmental Engineering Reference
In-Depth Information
Table 3.2
Specifications for the investigation of a suspected site with homogeneously distributed
diffuse soil contamination
Number of (composite) samples
to analyse
Number of borings
With observation
well
Soil (suspected
depth)
Surface (ha) Down to 2 m
Total
Groundwater
<1
5
2
7
2
2
1
6
3
9
3
3
2
7
3
10
3
3
3
8
4
12
4
4
4
9
4
13
4
4
5
10
5
15
5
5
6
11
5
16
5
5
P
5+
p
2+0.5
p
7+1.5
p
2+0.5
p
2+0.5
p
(hand driven) augers, the selection of samples in the field and sending these sam-
ples to the laboratory for chemical analyses. Consequently, they are appropriate
when there are no possibilities for the application of other techniques (e.g. magne-
tometry, metal detection, ground penetrating radar, seismic/acoustical techniques,
trial pits). However, application of those techniques often can deliver much more
information for similar costs that would otherwise have been spent on sampling
and analyses. Still, non-intrusive techniques and screening techniques are often
less sensitive as well as less quantitative. Consequently, these techniques are of
much more value when applied in conjunction with the more traditional method
of sampling and analysis. Indeed, in the development of international standards on
the application of screening techniques for the investigation of soil contamination,
the parallel use of traditional techniques to allow quantification of the results of
the screening technique, is considered as a boundary condition. Nevertheless, the
number of traditional samples and analyses can be diminished to a large extent
while at the same time screening methods provide the possibility of obtaining a
much more dense network of measurements and consequently a much better per-
ception of the actual soil quality. For the phase of the Exploratory Investigation, the
application of screening techniques, however, is less obvious, as the purpose of the
Exploratory Investigation is not to map the boundaries of the contamination, but to
acknowledge that an assumed contamination is indeed present.
Having performed the fieldwork and the analyses, the results of both activities
have to be interpreted in light of the hypothesis that was the basis of the applied
strategy. Often there is a tendency to accept the analytical results as being a bet-
ter representative result than the observations of the sampler. For example, when
the sampler has observed an “oil like smell”, it is often thought to be an incorrect
observation when the analysis for mineral oil does not prove that there is indeed a
contamination with mineral oil. In this case it is a familiar mistake to forget that the
analysis for mineral oil includes oil components with an equivalent boiling point of
more than C
10
, while the more volatile components might be present, but are not
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