Introduction to Contaminated Site Management - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 56

part of the region (the contaminated site), while the surroundings of the site remain
slightly contaminated. Therefore, the background concentrations are often declared
to be of (politically) acceptable soil quality, independent of the risks involved.
1.7.8 Spatial Scale
It is important to realise on what scale soil contamination needs to be considered.
When a backyard is contaminated, it is clear that the human health of the inhabitants
needs to be protected. In fact, for every contaminated site, the health of humans in
contact with the site must always be the primary focus. In many cases, ecological
protection will also be of concern. It is generally wise, certainly for the definition
of remediation objectives, to take the soil quality of the wider environment into
consideration. It often happens, mostly in urban areas, that remediation of small
contaminated sites results in a number of 'clean' sites in an otherwise (slightly)
contaminated area. This raises the question of whether human health has been suffi-
ciently protected in the slightly contaminated areas around the 'clean sites', since the
experts have found it necessary to reduce the risk at this specific sites to lower levels
than the individuals at the slightly contaminated sites are experiencing. The same
issues play a role in the case of a remediation that has taken place for protection of
the soil ecosystem.
Moreover, debate could arise about the cost-efficiency of several small-scale
remediations in the same area. A regional-scale approach offers possibilities from a
cost-efficiency perspective. It is often much less expensive, for example, to investi-
gate and perform Risk Management options for a larger area, in one big project, than
to do this in several smaller projects, at different moments in time. And in the case
of groundwater contamination, as another example, it is efficient to investigate and
manage all the sites that drain towards the same groundwater body and not just to
focus on management of the individual contaminated plumes. Moreover, since con-
taminated groundwater migrates, groundwater plumes have often intermixed, which
technically would not make a site-specific approach possible.
Another example in which regional-scale thinking is beneficial relates to soil
material transposition . Soil material transposition from an intensively used residen-
tial site to a less intensively used business park in the same area, for example, would
imply risk reduction for the whole area. Obviously, Risk Management is much more
complicated than this simple example shows, since more elements are involved than
just human health risks, for example, the effects of leaching into the groundwater
at the residential site and the business park and juridical aspects in case the loca-
tions are situated in different municipalities. However, the example shows that a
more regional approach offers practical possibilities for efficient contaminated site
management.
A specific example of regional Risk Assessment and Risk Management is the
dredging of sediment materials. When dredged materials are deposited on the site
of the water courses, the overall contaminant load stays the same within the area.
However, since the physico-chemical environment of the water-saturated sediments