Introduction to Contaminated Site Management - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 16

organisms of a wide variety. Soil includes two different entities, namely, a water-
unsaturated upper soil layer ( upper soil ) and a water-saturated groundwater zone.
These two entities are separated by a groundwater table. Typically, the gas phase
is absent in the water-saturated groundwater zone. From the perspective of ground-
water subtraction for the drinking water supply, a water-saturated groundwater zone
with high water volume and replenishing capacities is referred to as the aquifer .
Some definitions of 'soil' only refer to the water-unsaturated upper layer which,
depending on the depth of the water table, implies a layer of several centimetres
in swamp areas and up to hundreds of meters in arid regions of the world. Other
definitions, for example, from an agricultural perspective, link the term 'soil' to that
part of the earth's crust that is actually used by humans. According to this definition
soil usually includes the water-unsaturated upper soil layer and, often, the upper part
of the water-saturated groundwater zone.
This topic focuses on the impacts of contaminants. In this context, soil refers
to that part of the earth's crust in which contaminants reside that might impact
one of the protection targets. Impacts from non-private water supply (from deeper
groundwater or surface waters) are excluded from this topic, since it is assumed
that Waterworks sufficiently control the water quality. As a consequence, the scope
of this topic roughly coincides with the 'agricultural definition' of soil, that is, the
water-unsaturated upper soil layer and the first tens of meters of the aquifer.
For practical reasons, the terminology followed in this topic is linked with the
most common terms used in soil policies and management of contaminated sites,
see the schematisation of soil as defined from a wider perspective, in Fig. 1.4 .In

TERMINOLOGY
FOLLOWED IN
THIS TOPIC :

OFFICIAL
TERMINOLOGY :

Water-unsaturated
soil layer/
Unsaturated zone/
Upper soil layer

Soil

Water-saturated
soil layer/
Saturated zone/
Groundwater
zone/
(aquifer)

groundwater
table

Groundwater

Fig. 1.4 Schematisation of soil