A Practical Approach for Site Investigation - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 155

In addition to the investigation of the sites, the standard also contains three strate-
gies which aim at the determination of the soil quality of soils to be excavated in the
future:

•

The determination of the soil quality for uncontaminated soils.

•

The determination of the soil quality for large scale uncontaminated sites.

•

The determination of the soil quality for soils with a heterogeneously distributed
diffuse soil contamination.

The latter three strategies are to some degree comparable to the site investigations
for these types of sites, but comply with legislative boundary conditions set for the
reuse of soil lots in the Netherlands.
For each strategy, concrete instructions are formulated on:

• The sampling pattern.

• The maximum depth of borings.

• The soil layers that are to be sampled.

• The number of borings for soil sampling.

• The number of borings where monitoring wells are to be installed.

• The number of samples of both soil and groundwater that actually are to be

analyzed.

•

If soil samples are to be analyzed on an individual basis, or that the analyses are
performed on composite samples.

• The contaminants that are to be analysed in soil and groundwater samples.

Two examples of these sampling strategies are provided in Tables 3.1 and 3.2 .Itis
important to realize that the numbers provided in these tables do not have a scientific
basis. These are, as described before, thought to be a good compromise between the
costs of sampling and analysis in comparison to the type of contamination to be
investigated and the potential risk of missing a contamination.
As mentioned before, these strategies are based on the application of conven-
tional sampling techniques, thus by obtaining samples through the application of

Table 3.1 Specifications for the investigation of a suspected site with local soil contamination
with known location

Number of borings Number of samples to analyse

To 0.5 m under
contamination

Boring with
observation well

Soil from hot
spot Surface (ha) Groundwater

<0.01 2 1 1 1

0.01 ≤ 0.05 3 1 1 1

0.05 ≤ 0.08 4 1 1 1

0.08 ≤ 0.10 5 1 1 1