Environmental Engineering Reference
In-Depth Information
Fig. 23.4
The
source-pathway-receptor
causal chain
mechanism of environmental risk is often described in terms of a source-pathway-
receptor causal chain (Fig.
23.4
). This is one of the fundamental approaches to the
assessment of contaminated sites and development of solutions. In this context, the
source is the contamination in the soil or water and the pathway is the link of the
contamination and the effects at the receptors of concern.
In principle, risk reduction may be achieved by removing the source, by con-
trolling or eliminating the pathway, or by removing the receptors. Each of these
different approaches has a different interface with the three components of RBLM.
For example, at the simplest level of analysis, removing the source may use other
resources and have an overall negative impact on the environment. Control of path-
ways may have a lower initial resource use, but has long-term care implications.
Removing receptors may be costly or socially problematic.
23.7.2 Land Use Related Requirements
23.7.2.1 Practical Needs
Different land uses have different needs in terms of the condition of the site. For
example, some land uses require direct access to the soil, preventing the use of
surface containment measures like capping with concrete or asphalt. Others may
require the preparation of the site for geotechnical purposes, for example to support
foundations. This type of considerations can be combined with the “fitness for use”
principle, resulting in an assessment of “fitness for purpose”.
In some cases, the contaminated layers in a site may contain rubble, rubbish and
coarse waste materials requiring excavation for other reasons, such as construction
work. This could make excavation and removal an efficient solution to risk reduc-
tion. Often on-site recycling and re-use of debris is possible and can reduce demand
on primary aggregate resources in these cases.
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