Environmental Engineering Reference
In-Depth Information
areas. Therefore, before deciding about the investment of large amounts of money
in remediation, it might be expedient to invest in more advanced site-specific Risk
Assessment. So a combined approach, using Soil Quality Standards to streamline
the preliminary stages of an investigation and using site-specific exposure and Risk
Assessment to achieve some fine-tuning in later stages, may be the most appropri-
ate procedure. In fact the different approaches seem to converge to this combined
approach as experience with remediation of contaminated sites increases, as was
shown in the reviews by Ferguson (
1999
) and Carlon (
2007
). Current approaches in
Europe and USA are generally framed as tiered assessment procedures. Generic Soil
Quality Standards are used in the first tier as a “quick and dirty” preliminary assess-
ment tool. In second and higher tiers site-specific Risk Assessment is used which
involves modelling and measuring the actual exposure of targets of concern at the
site. Because generic Soil Quality Standards are just a tool in complex assessment
procedures and can be formulated in different ways in different countries, a direct
comparison of the numerical values of Soil Quality Standards without consider-
ing the complete assessment procedure and the underlying assumptions would be
misleading. Moreover the assessment procedure and the derivation of Soil Quality
Standards may also depend on country-specific political choices and geographical
elements. The study of Carlon (
2007
) took geographical and political elements into
account in order to make a comparison as realistic as possible.
The use of various Risk Assessment approaches and their scientific background
have been discussed in the CARACAS network. CARACAS observed that Risk
Assessment is not a fully-fledged scientific discipline on its own. It is a rather
loose assemblage of elements borrowed from various scientific disciplines. There
is a large need for further improvement and integration. Constructive discussions
with the NICOLE network (Network for Industrially Contaminated Land in Europe)
about the uncertainties in the assessment and the level of precaution to be applied in
view of the current status of assessment procedures led to the common position that
Risk Assessment is already a very useful tool, if one is aware of its limitations and
uncertainties.
23.4.3 Risk Management
Until quite recent times, the remediation of contaminated sites was based on civil
engineering approaches aiming at maximum risk control (excavation or contain-
ment). These approaches are still the fastest way to solve the problem. In a densely
populated country like the Netherlands there is heavy pressure on re-utilization of
contaminated sites, so fast remediation is an advantage. However, the high costs
associated with these methods are also a big disadvantage and were prohibitive in
many redevelopment projects. This has led to the exploration of risk-based solutions
which make use of natural capacities of the soil environment like immobilisation,
isolation and natural attenuation of contaminants. Remediation methods that make
use of natural capacities of the soil environment -or expressed in a more modern
way- ecological services of soil, natural attenuation, more specifically Monitored
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